Newly Added - Card Choices -> Weakest Cards and Specific Rules Section.

Please read the description (there's toggles). I'd suggest at least reading the sections: Overview of the Deck and Basic Play of the Deck if you don't want to read the whole thing. However, each section does help to explain the deck a little better, so if you have the time, I highly suggest reading it fully.

There's custom categories on the deck, which you can view by clicking one option in the pie chart to the right, and it will highlight the cards in that category. These categories will just help to give a quick overview understanding of the deck initially, so feel free to give that a peak.

The deck has become quite the toolbox deck (Summoner's Pact is a virtual copy of my creatures, allowing more than 4 of each one, and Primeval Titan does silly things with all the lands - view the Godhand section for some examples).

Scapeshift is also a strictly better Cultivator Colossus in almost every situation, provided you still run at least one copy of the creature. Bring to Light can become another copy of Scapeshift, Tibalt, Cosmic Impostor  or even one of our silver bullet instant/sorcery sideboard cards. Elvish Reclaimer is also an improved Expedition Map if you don't need to crack it same turn, since it is reusable and puts the land directly into play, while also being a threat that scales.

There's probably a lot of other cards that look like questionable includes, but if you read through the description, they are explained in greater detail throughout.

The basic play of the deck game 1 is to mulligan until some type of ramp, usually in the form of Amulet of Vigor and either multiple land drop cards or a fatty. You basically want to have a plan to have potential for around 6 mana by turn 3 (4 at the latest) when you look at your opening hand, or at least a bunch of little guys that synergize well and create board presence to block with. I've definitely had more than a few turn 3 wins with a 4 card opener, so don't be afraid to mulligan aggressively if you see no opening turns in your hand. The cards you want missing in a keepable opening hand are generally Amulet of Vigor and/or Primeval Titan. You need a basic mana engine and some board presence/hate if you don't have the ability to play an early titan. Reason being that Primeval Titan basically runs 8+ copies because of Summoner's Pact + Eladamri's Call + Tolaria West + Turntimber Symbiosis  and you don't actually need an Amulet of Vigor for your lands/creatures to produce value, it just gives them more value. I also suggest trying to keep a green bounce land in hand if you happen to have either an amulet or extra land play creature out, and are just waiting on the other piece. Generally speaking, the only time I play my last bounce is when I can hardcast an impactful creature the next time I untap.

Basically, try to get a Primeval Titan out as fast as possible (turn 3-4 usually). Once you cast the titan you can swing with it same turn (if you have an Amulet of Vigor out) after fetching Slayers' Stronghold and Boros Garrison or Hanweir Battlements   mana source, letting you grab even more lands. From there, the huge land toolbox will set up your future turns quite nicely, even if that titan was the only thing your hand had going for it. You can also fetch Hanweir Battlements  and Crumbling Vestige (or a bounce if you have another way to produce ) without an amulet if you have a bounce in hand and enough extra land plays to replay the Hanweir Battlements  for haste, or just want to keep an extra open mana after attacking.

In games 2 and 3 of a match, once you know the deck of your opponent, solid hate can be keep-able instead of the whole fatty plan. It really comes down to the opponents deck when you are deciding how to play the deck, because it can be played as just about any type of deck (tempo, control, midrange, combo, and even prison if you run some obscure options). I marked some of the more common targets to side out with #flexslot so you can have a better understanding of the core of the deck and some of the filler cards.

How you stack triggers matters. My general advise is to resolve things where you have no choice, first (so you stack them in the opposite order). I generally resolve my triggers as Vesuva copies (not a trigger, but you have to choose it first), Amulet of Vigor untaps, Mosswort Bridge hideaways, Crumbling Vestige color choice, Valakut, the Molten Pinnacle targets, then finally Simic Growth Chamber etc. bounce a land. It is very important to stack them so you have the most options available if a response happens, as sometimes how you stack things can make or break you (you can also play instant speed interaction before resolving some triggers, netting you extra information before making certain choices, or even something like Elvish Reclaimer as interaction with a bounceland to protect your land against land destruction).

A few important tips are that you can bounce utility lands (without an Amulet of Vigor) after fetching to replay and use them the same turn, even blow up your own lands with Ghost Quarter, and playing Vesuva as an untapped copy of nothing to produce mana with Dryad of the Ilysian Grove, to name some of the most overlooked lines of play. One other important thing is that Vesuva can only copy lands already in play, not lands found with the same Primeval Titan fetch.

Amulet of Vigor - one of the cards that makes this deck really shine, eliminating the downside of many of my lands, while also giving my titans +2/0 and haste (plus an extra land!). Multiples of this ramp me really fast, and is a force to be reckoned with.

Summoner's Pact - pretty much 4 more copies of Primeval Titan or whatever creature is needed, but be careful with the upkeep (I like to account for them potentially destroying any of my lands with a Tectonic Edge or the likes)!

Scapeshift - capable of winning games with Dryad of the Ilysian Grove or Amulet of Vigor + 6 lands out by finding Valakut, the Molten Pinnacle or setting up a (usually) game winning Cultivator Colossus by finding Bouncelands + Tolaria West. With only 5 lands and Amulet of Vigor out, you can run away with the game by transmuting into Primeval Titan in pretty much the same way, depending on which lands you have to sacrifice. It can also function as mana-fixing or ramp depending on the situation as well. Not really the greatest thing in multiples, since most of our lands are important utility lands, but definitely a lot of synergy with the deck overall. It generally ends up a cheaper Cultivator Colossus or Primeval Titan, but sometimes one of your lands in play were important, so it's not always game winning on the spot (we help to mitigate this by running both Hanweir Battlements   + Slayers' Stronghold). It's also pretty horrible without Dryad of the Ilysian Grove or Amulet of Vigor, so it isn't ideal against decks with interaction.

Bring to Light - tutor for any 3 drop or lower creature, or even Scapeshift to tutor into a threat with Tolaria West. It essentially works as Eladamri's Call where you put the card into play, but instead of finding something larger than 3 CMC, we find Scapeshift instead. Without Amulet of Vigor for the Scapeshift line, we will look for Valki, God of Lies  to play as Tibalt, Cosmic Impostor  or Dryad of the Ilysian Grove / some other creature.

Honorable Mentions

Fae of Wishes / Wish / Glittering Wish - even though Fae of Wishes is technically a creature, it's adventure mode is a non-creature spell, which is what we are interested in mainly. This is the most relevant of the wish cards, since we can still cast it for the adventure mode when hidden away, and it has extra synergy when hit with Turntimber Symbiosis   for a 4/7 flier. You could also abuse the discard mechanic if you were running some grave tech like The Gitrog Monster and/or Crucible of Worlds. Wish is just the most flexible wishing card, letting you grab literally anything. However, it forces you to use it the same turn, so often it isn't as ideal as some other wish options. Glittering Wish is a tutor for anything multicolored in the sideboard.

Tibalt, Cosmic Impostor  / Savor the Moment - Savor the Moment is one card that is mainly for enabling other cards, but it usually isn't horrible to draw into either. Skipping your untap step sounds like this card doesn't do much, but it is actually a nice fit for this deck (worst case, an overpriced Explore). It essentially reads as: "Draw a card. You get an additional combat step. Reset your lands played for the turn to 0." That's actually crazy value for the deck, especially late game. Tibalt, Cosmic Impostor  serves the same purpose, but is less reliant on having other cards to make it good. It creates card advantage, and can be spot removal, being a very versatile target. It is also conveniently a target at 2 colors, so it can always be found. This makes both a great card to hideaway with Mosswort Bridge, or to find with Bring to Light if you don't have the presence for a Scapeshift line.

Growth Spiral / Explore / Growth Spasm - The main benefit to Growth Spiral over Explore is if you have any lands that can be used in response to something else, for example Sejiri Steppe for protection of a creature, any bounceland as protection against land removal, or an activated Valakut, the Molten Pinnacle that you can use as removal for your opponent's creatures/planeswalkers. You can also use it for extra information in response to a Simic Growth Chamber trigger, allowing you to bounce a different land, or sneak in the one in your hand to reuse, etc. The extra color restriction can backfire, so it is a slight trade-off. Growth Spasm lets you essentially ramp 2 extra mana, and gives a blocker in a pinch.

Manamorphose - color-fixing where the main downside is not knowing what card it "really is" when considering your hand for a mulligan. It also doubles as a pseudo-answer for Blood Moon as a happy coincidence.

Eladamri's Call / Threats Undetected - Even though this isn't quite as good as Summoner's Pact in most situations, they are both solid tutors. Eladamri's Call lets you tutor for any creature, which is often the missing piece in the puzzle (solid turn 2 if manabase supports it). Threats Undetected will let you find two relevant creatures, which lets you go over the top of your opponents (requires enough targets).

Escape to the Wilds - Pretty close to a draw 5 card with an extra land play tacked on, since we can use the extra lands unlike a lot of other decks.

Heartless Summoning - this is very comparable to Amulet of Vigor in what it does for the deck. It allows me to play my creatures faster and for less. However, unlike Amulet of Vigor it is very bad in duplicates, so 2 copies at most. It also doesn't synergize very well with Mosswort Bridge so definitely a far worse acceleration card.

Karn, the Great Creator - This is another "wish" option, he's just in an awkward spot of the mana-curve. 4 CMC is an awkward spot for this deck, as you generally jump from 3 to 5 or more relatively quickly. However, Karn, the Great Creator mitigates that with his -2 which let's you grab any artifact from your sidedeck and potentially play it in the same turn helping to have an outlet to spend your mana on. He also can be very relevant artifact hate, both with his passive and +1 which is lowkey removal for any artifacts that are or / .

Primeval Titan - the main creature this deck revolves around, quite the force to be reckoned with. It often comes out as a 8/6 haste trample vigilance, after fetching Boros Garrison and Slayers' Stronghold with at least 1 Amulet of Vigor out (each multiple means it gets another +2/0). Also, even if it gets removed, you get the land triggers, so sometimes playing into removal is the correct play, and ignoring haste.

Cultivator Colossus - This is basically Primeval Titan's big brother when your hand is mana flooded or a utility land you need is in your hand instead of your deck. It doesn't quite go infinite with bouncelands since you need to fully resolve Cultivator Colossus's ability before resolving anything else, but it is definitely a way of making the most of mana-flooding, letting you draw into things to spend that mana on. This is significantly worse than Primeval Titan if you don't have at least 2 lands in hand. If you have 4+ lands in hand, I would say it is generally better. With 3 lands in hand, they are generally equivalent, with certain boardstates preferring one option over the other.

Arboreal Grazer / Sakura-Tribe Scout / Sakura-Tribe Elder - First there's the 1 drop creatures with slightly different uses. Arboreal Grazer is actually fetchable ramp in a sense, because it can net you 1+ extra mana in a lot of situations with a Summoner's Pact (not a suggested path against interaction). It also has reach and makes a decent blocker afterwards. Sakura-Tribe Scout is a little different, since it does nothing the turn you cast it. However, the tap effect is not only reusable every turn, but it can also let you play lands as a response to actions, similar to Growth Spiral (for example Sejiri Steppe for protection of a creature, any bounceland as protection against land removal, or with an activated Valakut, the Molten Pinnacle that you can use as removal for your opponent's creatures/planeswalkers). Sakura-Tribe Scout is also capable of ramping you to a turn 4 Primeval Titan on its own, with no other acceleration in hand. Sakura-Tribe Elder is something you can block with, then sacrifice it, for "ramp" the turn you draw it, with the basic land being resilient to removal/hate and helps a bit against Blood Moon.

Elvish Reclaimer - Surprisingly, this versatile guy is really good at just about everything. It can act as a psuedo-extra land card, a land tutor, a sizable threat to stabilize when you have nothing. This is a 1 drop that scales up as the game goes on, and can also be used as a tutor for the land you really need (really good at finding your missing bounceland or Urza's Saga). You can also use the activated ability in response to the triggered ability of Urza's Saga's 3rd chapter to basically replace/upgrade your land in addition to searching for your artifact of choice.

Azusa, Lost but Seeking / Dryad of the Ilysian Grove / Wayward Swordtooth- Azusa, Lost but Seeking is two additional land drops per turn, which enables Primeval Titan the turn after pacting and having 0 open mana with an amulet and bounceland. However, she is legendary, so you never want more than 1, which is why I generally run 1-2 copies of her. Dryad of the Ilysian Grove is an additional land drop every turn, mana-fixing, and a solid 2/4 body for 3 mana. It also combos with Valakut, the Molten Pinnacle as a win-condition. Wayward Swordtooth is resilient to red removal due to its high toughness. Its high power can also help with Mosswort Bridge even if it can't attack or block. Definitely the weakest of the three in most situations, but it does have its scenarios.

You can't really fill the deck with too many utility creatures and Elvish Reclaimer is a borderline card that is sort of a utility creature / ramper in certain scenarios, so if you are running it, make sure you keep utility creatures to an absolute minimum.

Honorable Mentions

Eldrazi Displacer - This card is capable of a lot more than you think at first glance. Its activated ability is where we are interested, which is flexible, because it can be used on both our creatures, and our opponents creatures. Also, since we have Amulet of Vigor this can also act as a psuedo-vigilance for us, while tapping down our opponent's creatures. It is usually best served when activated on one of our creatures with an ETB trigger, but there's other combat trick / protection usages as well. Of note, you can blink your titan, finding to loop for deck thinning, basically guaranteeing a hit with Mosswort Bridge later (start with Crumbling Vestige + Valakut, the Molten Pinnacle if you have Dryad of the Ilysian Grove to sneak in some extra damage). You can also use it similarly to refill your hand, or even find protection like Sejiri Steppe or some other utility land at instant speed. This can enable a lot, while also essentially being a double blocker on its own, so it isn't strictly a combo piece. It is also capable of ramping with multiple Amulet of Vigor or drawing loads of cards with Cultivator Colossus.

Omnath, Locus of Creation / Soul of Windgrace - if you can somehow support the greedy casting cost in here, both are worthy of inclusion. Omnath, Locus of Creation is one of the best landfall creatures ever created, and Soul of Windgrace can be seen as a creature version of a planeswalker, for all intents and purposes. I tried them for a while, but found if I could get to their manacosts, I could get to almost as easily, so I found there's generally better options by the time we have access to the casting cost.

Tireless Tracker / Courser of Kruphix / Radha, Heart of Keld / Augur of Autumn / Ramunap Excavator - Tireless Tracker is slightly different than the rest, but I would say it probably fights for this slot the most. It is a form of card advantage that is capable of growing itself, although at the cost of investing further mana, unlike some of the following options. Courser of Kruphix is good at letting me eliminate land draws, which can really be a problem sometimes. It also is Lightning Bolt proof, which can be huge sometimes. Lifegain from lands hitting play is just icing on the cake. Augur of Autumn / Radha, Heart of Keld does basically the same thing as Courser of Kruphix, but they are geared more towards grindy control matches instead of aggro decks, since they don't broadcast info. Augur of Autumn can let you play creatures from the top of your deck as well if you have 3 creatures with different power, while Radha, Heart of Keld can pump itself up to be a sizable threat. Ramunap Excavator is slightly different from the others, as it enables playing lands from our graveyard, instead of the top of our decks. Something that is also very relevant for them all is that its 2+ power can be just what's needed for that Mosswort Bridge activation.

Springbloom Druid / Mina and Denn, Wildborn / Oracle of Mul Daya / The Gitrog Monster - Springbloom Druid may seem slightly different than the rest, but for all intents and purposes it accomplishes basically the same thing as an extra land play for the turn, while helping against Blood Moon. Mina and Denn, Wildborn is a fatty that can give trample, while Oracle of Mul Daya is built in card advantage and an alternative way to use our land drops. The Gitrog Monster is an additional land drop, card advantage, and a decent body all wrapped up into one package. It's also nice to have a relevant 5 CMC card to fetch with a Summoner's Pact when I fall just short of the 6 CMC Primeval Titan - the only downside is sometimes it forces me to pitch a land I'd rather not or it ends up keeping you in a 1 mana short cycle where you are stuck at 5 mana due to having to sacrifice a land every turn.

Lotus Cobra / Tireless Provisioner - Lotus Cobra helps to produce extra mana of any color with all of our land drops. Lotus Cobra is more of a combo deck option, and can almost be viewed as a worse Amulet of Vigor for mana purposes. Another thing that is relevant is that its 2 power can be just what's needed for that Mosswort Bridge activation. It can also be found with a Summoner's Pact when you opponent is completely tapped out, and you could cast a Primeval Titan already, since you'll get back your two mana on the first fetch. Tireless Provisioner is very similar, except it also can create food tokens, and "store" mana across turns, since you don't have to use your Treasure tokens right away.

Questing Beast - surprisingly this card is another solid option for a lower CMC bomb. It makes a good blocker even as you chip away at their life points due to vigilance. It can also chip away at their swarm, or deter them from swinging with the fatty due to deathtouch.

Nethroi, Apex of Death - a solid body on a 5 CMC with deathtouch and lifelink, basically a mini Wurmcoil Engine. However, Nethroi, Apex of Death really shines for its mutate ability against removal. If you have enough mana, instead of finding another Primeval Titan with your Summoner's Pact that you transmuted from Tolaria West, you can find this guy and bring back most if not all of what they removed.

Woodland Bellower - pretty decent option with the variety of 3 CMC and below creatures that are viable in this deck.

Tolaria West / Turntimber, Serpentine Wood  / Port of Karfell - Tolaria West can transmute into another Summoner's Pact for whichever creature fits your situation best. It can also become any land, a Chalice of the Void or Engineered Explosives if either is in the deck (or any other 0 CMC sideboard card). Turntimber, Serpentine Wood  is basically a land that doubles as a threat with any bounceland later in the game. It is very comparable to Tolaria West in functionality, except it cannot be fetched by Primeval Titan and is a much preferred untapped green source when needed (notable when trying to stretch your manabase a little too much). Port of Karfell is basically recursion of a titan that's uncounterable in most situations. It is a decent option for the slot in more control oriented metas if you are in those colors.

Valakut, the Molten Pinnacle - this is actually a win-con with enough land drops and Dryad of the Ilysian Grove. Due to the Bouncelands being able to bounce themselves, you are generally able to utilize all your extra land drops on each turn, so this damage can add up really quickly. It can be used to clear the board or to do direct damage.

Crumbling Vestige / Vesuva - these are basically a mandatory include because of all the great plays it enables. You can produce mana without an Amulet of Vigor out off a Primeval Titan fetch. You can also go +1 land with Crumbling Vestige + Slayers' Stronghold instead of Boros Garrison + Slayers' Stronghold when you have Dryad of the Ilysian Grove out, and sometimes that one land can be the difference that enables more burn damage with Valakut, the Molten Pinnacle. It can also be used to leave an extra mana open after attacking, by getting Hanweir Battlements  allowing you to have at least 5 open mana after attacking when finding 2 bounces (perfect for Bring to Light in your second main once you have more lands). Vesuva is probably the best land in the deck, as it can be pretty much anything. In addition to copying anything (opponent's lands included), you can play it untapped copying nothing with Dryad of the Ilysian Grove out to produce mana, an often overlooked line of play.

Boseiju, Who Endures - One of the best utility lands for the deck, since we can easily bounce it back to hand, making it fetchable removal for artifacts, enchantments, and even troublesome lands (essentially a broader version of Ghost Quarter if you don't plan to use it on yourself). It does technically ramp your opponent in most cases, but that's a fair tradeoff for eliminating a more troublesome permanent.

Cavern of Souls - good for control matches, and it can also be useful for colored mana when trying to hard cast more color intensive creatures like Sigarda, Host of Herons. Since we have a lot of bouncelands in here, we can change the creature type named almost as often as wanted, so this is almost like an Ancient Ziggurat that can tap for colorless when not casting creature spells.

Slayers' Stronghold / Hanweir Battlements  - some of the best utility lands for this deck. It allows your titans to come out with haste, you can't really ask for more. Slayers' Stronghold is the better of the two, since it gives haste/vigilance and +2/0, which can be important with enabling Mosswort Bridge triggers. Having both as an option gives you a lot of flexibility in your plays, and makes us less susceptible to things like Surgical Extraction or drawing into our only haste enabling land before playing the titan. Be careful not to overcommit to non-green lands though, as you need green lands for the deck to function early. I generally suggest choosing at most 2 between these and Sunhome, Fortress of the Legion as you don't want colorless sources as much.

Sunhome, Fortress of the Legion / Sejiri Steppe / Mosswort Bridge - Sunhome, Fortress of the Legion is great to block something with deathtouch (take that Wurmcoil Engine - I live and you don't even gain life), or just double your damage. However, Sejiri Steppe accomplishes one of the main goals of this utility slot, which is to help your Primeval Titan live after attacking (against most decks), but it requires no investment of to activate. This slot is unneeded in some matches, so it can easily be sided out when it's not that relevant. Sejiri Steppe + Mosswort Bridge cover the defensive and offensive purposes of Sunhome, Fortress of the Legion in almost every situation, without the need of as much mana investment, even allowing more aggresive plays sometimes, all while being colored mana sources instead of colorless. Mosswort Bridge is the most powerful digging tool and virtual advantage this deck has to offer. Cast off anything for 1 green? Yes please! Need to find some removal because they are just stalling with something stupid and annoying? Keep copying/bouncing this until you find what you are looking for. Another thing worth mentioning is Mosswort Bridge + Vesuva in conjunction with any bounceland becomes a powerful digging tool (hide multiple land drop cards/ways to play titans to get bounces until you find your answer). Also, this lets us cast Fae of Wishes or any other Wish variant at instant speed if it is hidden away. I used this trick a lot with Batwing Brume and Glittering Wish when Splinter Twin was prevalent to just win games during their attack phase when they thought they'd won. If you are running Mosswort Bridge, it is basically required to run Slayers' Stronghold + Boros Garrison alongside it, allowing you to get to 10+ power far more consistently. Because of those mandatory inclusions, Sunhome, Fortress of the Legion is a basically equivalent option as well, being in the same colors. Also worth mentioning is that you can use the hideaway of Mosswort Bridge to exile cards you don't want to draw, if you whiff, or don't plan on activating it prior to bouncing it back to your hand. After a shuffling effect, this deck-thinning helps increase your odds of hitting cards you want by a few percentage points.

Castle Garenbrig - this is decent as potential ramp if you run enough fetches + Forest Subtypes that it can consistently come out untapped. Not really worth forcing into the deck, but it can be viewed as +2 for mana calculations in a lot of scenarios, so definitely a solid include.

Urza's Saga - I've finally given in and invested in a playset of Urza's Saga due to the early plays it enables game 1. However, I don't think it is good enough of a card that you necessarily need to run a full playset (I fluctuate between 3-4 copies). If you have to rely on Urza's Saga to find Amulet of Vigor, your hand wasn't amazing anyway. I still maintain it is over-hyped and super vulnerable to removal (you basically concede against an early Blood Moon, Magus of the Moon, or Force of Vigor). However, one thing the saga does well is allow for a double amulet more often (making it a solid turn 1/2 land). One additional upside the Saga does have going for it is the negatives aren't really preyed upon until games 2/3 of the match making it a powerful game 1 tool. I also don't run Expedition Map alongside this, as it's only decent alongside a full playset of sagas (I don't think it is worth it if not playing 4 copies), and you'll often find Amulet of Vigor instead in almost every situation anyway. I think Elvish Reclaimer does a much better job than the map, all things considered (way more versatile + puts the land into play instead of hand, so it enables interactive plays).

Forest / Snow-Covered Forest - basic lands are needed, enough said. It stops Path to Exile from being as devastating, and allows some powerful interactions by targeting yourself with Ghost Quarter, along with giving hope against Blood Moon. I typically like to use white bordered basics to make fetching easier (you can fan out your deck instead of going card by card) if going with fetchlands, just a little trick I like to use to help speed up games.

Selesnya Sanctuary / Golgari Rot Farm / Simic Growth Chamber / Gruul Turf - green bouncelands, the main thing this deck revolves around. It is a good idea to keep one of these in hand at all times (or a Vesuva to copy one) to make the most of your multiple land drop potential. The only time I play my last one in hand is if it means I can hard cast a bomb that I feel will get through when I untap next turn. Otherwise it is best to keep one in hand with the potential of drawing extra land cards, allowing you to "go off" in a lot of cases (considering you have either an amulet in play, or dryad/azusa in hand, and are just waiting on the other piece).

Honorable Mentions

Verdant Catacombs / Overgrown Tomb / Zagoth Triome - Fetches / Shocks / Triomes just enable better mana fixing, landfall triggers, and deckthinning. The triomes can also become card draw when bounced if needed. You should generally pick 5 color lands or fetches, it's a little hard to support both. I generally go with fetches alongside at least one shock, because you still have all the untapped potential, but can choose for them to be tapped sources as well, to make the most of multiple Amulet of Vigor lines.

Aether Hub / Gemstone Mine / Tendo Ice Bridge / City of Brass / Mana Confluence / Vivid Grove / Nurturing Peatland / Yavimaya, Cradle of Growth / Reflecting Pool / Twilight Mire - Gemstone Mine is probably the best of the rest, since you can use it twice then bounce it to reset its counters. Aether Hub is a strictly better version of Tendo Ice Bridge and is next in line, since you can bounce it and replay it without using the to stack multiples for later. City of Brass deals 1 damage whenever tapped and Mana Confluence allows you to pay 1 life for any colored mana, which are very important distinctions, and here's why: City of Brass will deal damage to you no matter if you have a replacement effect on it or not, so things like Yavimaya, Cradle of Growth or Dryad of the Ilysian Grove don't help you. However, since it is damage, and not loss of life, it doesn't conflict with Elderscale Wurm or Worship. Mana Confluence is the complete opposite, so if you use it's mana ability with Elderscale Wurm out and go under 7 life, his ability doesn't prevent it, and you are basically vulnerable again. Vivid Grove comes into play tapped, essentially making it the worst of the bunch as it can sometimes takes away strong turn 1 potential. The draw-land cycle of cards like Nurturing Peatland is one land that actually isn't terrible to draw when mana-flooded. Yavimaya, Cradle of Growth gives all lands the ability to tap for which allows the deck to stretch it's manabase a little thinner. The filter cycle like Twilight Mire helps manafix if you have a lot of non-green double cost cards. Reflecting Pool is basically a psuedo-5-color land that makes cards with multiple of the same color cost a lot easier to cast. It gets exponentially better with more multicolored lands, and is quite nice in greedy manabases like this one.

Lair of the Hydra / Oran-Rief, the Vastwood / Turntimber Grove - Lair of the Hydra is a green land that is untapped when you need it early, so basically another Forest. However, this is a manland, which can let you pump your total power on a titan fetch, or become a threat on its own. Oran-Rief, the Vastwood is great with the prevalence of Unholy Heat in the meta, being able to protect a Primeval Titan by just leaving it untapped, or just pumping creatures, sometimes enough for a Mosswort Bridge activation. Similarly, Turntimber Grove works pretty much the same, but it is better on the titan fetch (being able to pump and tap for ), but is not reusable every turn without other support.

Lotus Field / Flagstones of Trokair - Typically these two lands are a package deal, as they are a nice fetch-combo when you need lots of mana. These are capable of producing 5 mana per Amulet of Vigor and still netting you +2 lands for your Valakut, the Molten Pinnacle triggers when fetched. Lotus Field is also capable of pumping our Elvish Reclaimer on its own (can be used after blocking). Flagstones of Trokair being a non-green source, and Lotus Field decimating your land count on their own are substantial downsides to consider, so you need enough synergy to justify inclusion of these. You'll often see these alongside Elvish Reclaimer due to the great synergy.

Crystal Grotto / Temple of Plenty - scry lands. If there's not a whole lot of early plays that need a turn 1 untapped land in your 75, the scry outweighs the slower land in most cases. Crystal Grotto is Zhalfirin Void 2.0, which can let you mana-fix as well, now giving you a relevant untapped version of the temples.

Ghost Quarter / Field of Ruin - land destruction that can double as another copy of a Forest if facing hate like Blood Moon. It's worth mentioning - don't hesitate to blow up your own lands with Ghost Quarter for landfall or The Gitrog Monster triggers - this has saved me on numerous occasions. It is actually a 3 mana land when fetched by Primeval Titan with Lotus Cobra or Tireless Provisioner out (two landfalls + green). It also allows you to draw 2 cards with The Gitrog Monster (one on the sacrifice cost, then one on the land destruction). In most cases, Boseiju, Who Endures is superior due to the added flexibility, but these are still solid options worth mentioning, especially if you have a way to recur lands from your graveyard. Ghost Quarter is especially good against something that lets you play lands from the graveyard, completely decimating your opponent's access to splash colors.

Khalni Garden / Radiant Fountain / Kabira Crossroads / Blossoming Sands cycle - chump blocker or lifegain slot. Sometimes that is enough to turn the tide of battle, so it isn't to be under-estimated as a utility option. I generally go with Khalni Garden / Kabira Crossroads if I have enough space (can potentially filter the with Wooded Bastion).

Blast Zone - This is more of a utility land to deal with the decks that pump out tons of low cost creatures/board presence. This is basically an Engineered Explosives attached to a land. It's biggest drawback is that it can't hit 0 cost permanents, since it enters with 1 counter on it already. You can also use it to blow up some big hard to remove threat with hexproof/shroud if you have enough mana.

Arena / Quicksand / Eiganjo, Seat of the Empire - targeted removal with their own respective pros and cons. Notably, Arena + Sejiri Steppe have decent synergy as a Primeval Titan fetch package. However, Arena not producing its own mana is the main thing holding it back, so you should consider it as more of a fetchable creature removal than a land if trying to fit it in. Quicksand is probably my favorite of the bunch.

It's important to be realistic about the deck, and point out what are the weakest/most unneeded cards currently. I'll point out what I want them to do for me, and why I don't think they are "ideal." Feel free to discuss other options or suggest replacements

Valki, God of Lies   - He's mainly in here as a Bring to Light target when Scapeshift isn't good. It just feels bad to draw into this particular card. I need something for this slot, and the fact that he can be found on only 2 colors is quite nice. He is definitely overpriced at 7 mana, realistically powered around most 5 mana planeswalkers, but a slightly worse option than other big mana avenues. This could be replaced with some 4 CMC powerhouse like Omnath, Locus of Creation / Soul of Windgrace / Phyrexian Obliterator or even something that is conditionally good (at different times from Scapeshift) like Savor the Moment. Nothing I've tried has felt correct, so I'd definitely say it is the weakest slot right now.

Wayward Swordtooth - Honestly, most of the time this is just a play an extra land card that can't block or anything. It is relevant to enable Mosswort Bridge sometimes, but most of the time you would much prefer something with added value like Dryad of the Ilysian Grove or Azusa, Lost but Seeking. I do prefer the reusability every turn over something like Arboreal Grazer for the slot, and it's also worth mentioning I don't want to run a second Azusa, Lost but Seeking because that legend rule comes up so much more often than you'd think it would due to our digging power of Mosswort Bridge.

Our second copy of Tolaria West - One copy is generally enough to win, unless playing against a more interactive deck. Drawing into it generally feels bad, and this is probably one of the first lands I'd swap for something else. For example, Port of Karfell fills the same basic slot in a better way for most situations, the only thing it doesn't do better is if I transmute for a second titan when Tolaria West got me the first one, or want to Scapeshift away the first Tolaria West and still be able to transmute a second one. Also if their removal is exiling, it is a definite feels bad moment, I would probably make the swap if Solitude wasn't a thing.

Mosswort Bridge is also a land that isn't completely necessary. I run it as my "I win" land over Sunhome, Fortress of the Legion mainly since it is less mana investment and opens up more interesting lines of play. However, it is reliant on more than just mana, so depending on how interactive the meta is, you may want to run Sunhome, Fortress of the Legion or neither option (the slot isn't 100% needed honestly, it is just nice to have).

Carnage Tyrant - sometimes this card feels like overkill against control. It may not be completely needed, but with skimping on some of my other anti-control options, uncounterable is a crutch I like to lean on.

Culling Ritual - probably one of the most irrelevant sideboard options, since there's not a whole lot of swarmy decks anymore, and it hits our own Amulet of Vigor. That being said, when it is good, it is amazing. It does cover us against most artifact/enchantment decks as well, since they generally center around lower CMC options. Additionally, it allows us to play a bomb with the ramped mana after clearing the board and is even findable with Bring to Light which gives it some extra value.

In my current sideboard, your main consideration should be where to double up on hate and where not to. You also want to consider which cards are strictly wish targets (if running any of the options), and which cards you can actually side in. Siding in your targets enables you to have a faster response, so that is generally the preferred line. This means you don't go heavy on cards which are only good when wished for.

My biggest suggestion is to try to have a tutor-able target for your major issues when possible (Summoner's Pact and Eladamri's Call function as tutors for creatures). There's a lot of smaller synergies with lands, since we can play them at instant speed with Sakura-Tribe Scout or tutor them up with Primeval Titan / Elvish Reclaimer but you shouldn't rely on those paths as your only answers, since they are less reliable to have access to early. Think of land hate in this deck as more coincidental than something you can rely on, even with all the tutor options.

I would order your preferred hate cards as:
Green Creatures - 1 card is 6+ virtual copies (Summoner's Pact / Tolaria West / Eladamri's Call)
Everything Else

Boseiju, Who Endures - in addition to being a land if I need the land drop that badly, this is hate for basically anything other than creatures and planeswalkers. It does ramp my opponent, but that's generally a fair tradeoff.

Dismember / Path to Exile / Condemn / Spirit Link / Vampiric Link - some of the best creature removal in the format. Spirit Link / Vampiric Link may look off here, but it is almost the same as removal when enchanting your opponent's non-utility creatures (can be better when dealing with blocking, but doesn't help against lethal or infect). It can even stack with lifelink on your own creatures for a psuedo "double-lifelink" effect.

Veil of Summer - the second best option against targeted discard (Leyline of Sanctity is generally better). This is also useful against counterspells or blue/black removal, and can be a nice cantrip against blue/black decks in general (U/B Mill doesn't really run counterspells, but this is still a nice include against them as some mill cards still target). This often acts as the two most commonly played options on Cryptic Command for only , making it extremely powerful when used correctly.

Endurance / Rest in Peace / Unlicensed Hearse / Relic of Progenitus / Turn the Earth - Endurance is preferred mainly due to it's evoke cost and the ability to be found with a Summoner's Pact. Even when you are tapped out, you can find this card and essentially counter anything if it is going to be game-ending by exiling another green card in hand. It can also be used on yourself to help in the mill matchup, unlike some other options (I only run one copy to not expose ourselves to Surgical Extraction and Extirpate as much since we have lots of creature tutor options). Rest in Peace is some of the best gravehate in the format, since it gives you a replacement effect moving forward, basically invalidating all graveyard strategies. Unlicensed Hearse has better interaction, being twice as powerful, and letting you choose the targets, along with being a potential threat on its own, while Relic of Progenitus is able to cantrip itself, and is findable with Urza's Saga. Turn the Earth is like a mini Endurance, except it works even when your opponent mills it, and can be used twice if drawn into. I like to run at least one copy of it in a mill heavy meta, since it is still a great gravehate card too. It's also worth mentioning that Turn the Earth is one of our forms of hate that is harder for decks to interact with than the artifact/enchantment options.

Engineered Explosives - targeted CMC removal. Being findable with Tolaria West, gives it extra value in the deck.

Force of Vigor - some of the best artifact and enchantment removal in the format. Capable of removing 2 problem permanents at the cost of 2 cards and no mana, this option definitely keeps some unfair decks in check (ours included, as this is one of our problem cards).

Culling Ritual - one of the best mass removal spells, since it can actually ramp us into our payoff cards if we are far enough behind, completely changing the pace of the game. This hits all troublesome permanents, so is often our hate of choice against artifact/enchantment based decks, since a majority of those cards are low CMC. It does hit our own Amulet of Vigor as well as some of our earlier cards, but thankfully we can cash them in for mana to play something else.

Unmoored Ego - a universal silver bullet against almost every combo deck, where you can attack their manabase, payoff cards, or paths to the combo, completely removing them.

Honorable Mentions

Worship - some sneaky tech that can buy us enough time to get back in the game in most cases. It's not really the best thing to try for, as you are dangerously close to death for it to take effect, but effects like these are capable of turning games around on their own. Since we can wish for it, then cast Fae of Wishes from exile to enable it, this is a pretty decent option to pivot a game you feel slipping away. It is actually really solid tech against RDW variations, as they don't expect troublesome enchantments from us, and will mainly pack artifact hate, or use their removal on Dryad of the Ilysian Grove instead.

Hokori, Dust Drinker - this lets you shift into more of a prison-style gameplay. It's a shame it isn't green and the cost is a little hard to consistently have early. If you play this while your opponent is tapped out (and they aren't an aggro deck or don't have a crazy board state) you basically win. This card hits most "fair" decks hard, but barely affects us because of Amulet of Vigor + Bouncelands, turning it's effect into more of a 1 sided Winter Orb. You basically transition a combo-deck into a prison deck with this sideboard option. Most non-aggro decks just aren't ready for that in modern and can't recover fast enough. Since most of the current meta is aggro oriented, this card isn't positioned very well in the meta. However, in a slow meta, this is some top-teir sneaky tech.

Chalice of the Void - very powerful denial against decks that are efficiently mana-curved, as most modern decks are. This is one that is best played early for 0 or 1, maybe even 2 if facing a hatebears/goodstuff kind of deck. It doesn't deal with any current threats at that CMC, it only prevents future ones from being played. This also hits your own cards as well, so be careful about that. It is findable with Tolaria West, giving it extra value in the deck. If you run lots of 0 or 1 drops, this gets a lot less valuable, as it is a double-edged sword.

Elderscale Wurm / Empyrial Archangel / Hornet Queen - I found myself being able to cast off a Summoner's Pact for a Primeval Titan in a lot of situations against more aggro builds, only to realize it didn't matter since I was dead the next turn anyway. Elderscale Wurm and a lot of the following options help to solve that, albeit in different ways. Everything has their specific situations and pros/cons, which I will try to explain. Elderscale Wurm just makes you invulnerable to damage until it is either removed or you drop below 7 life (loss of life bypasses the protection). Empyrial Archangel has shroud, which really comes in handy against removal. One thing worth noting is that the replacement effect is not optional, so they can remove it by simply doing 8 damage to you in 1 turn, probably its biggest downside to consider. Hornet Queen is less vulnerable to targeted removal, but more vulnerable to wipes due to low CMC and toughness. However, an army of deathtouch blockers will often slow/stop the opponents deck for a bit.

Dragonlord Dromoka / Sigarda, Host of Herons / Carnage Tyrant / Thrun, the Last Troll / Cragplate Baloth / Gaea's Revenge - first is Dragonlord Dromoka, whose lifegain and a high toughness make it an excellent blocker, as well as a tough to deal with beater thanks to flying. It's signature ability removes all interaction during your turn (other than activated/triggered abilities). Next we have Sigarda, Host of Herons who is near impossible to remove once it is down, so using something like Cavern of Souls to make it uncounterable is often the end of control players. There's other options like Carnage Tyrant / Thrun, the Last Troll / Cragplate Baloth / Gaea's Revenge which all basically have the uncounterable and hexproof combined, but I often prefer the added evasion of flying (and other abilities).

Wurmcoil Engine / Inferno of the Star Mounts / Inferno Titan - mainly for Blood Moon matchups, although they all have other uses as a solid uncounterable threat, resilience against removal, or pinger (killing Magus of the Moon on entry), which helps with the intended use since most Blood Moon decks tend to play counterspells and removal too. The firebreathing ability also gives you something to do with all that red mana, if you aren't able to deal with Blood Moon. Wurmcoil Engine is more relevant in other matches since colorless is a lot easier for our manabase to support, and is a resilient to removal option.

Plains - This is just a land to side in, when I side out Urza's Saga. I mainly chose it because I like the artwork, by no means is this a necessary inclusion. That being said, an off-color basic does help with splashing vs. Blood Moon and has synergy with fetches, Sakura-Tribe Elder and Springbloom Druid making them into better mana-fixers.

Sundering Titan - since we only run the Forest subtype, this is an all-star against a lot of multi-colored decks, letting us destroy multiple lands and playing a threat at the same time. If it dies, you get to destroy lands all over again. Its usability is diminished a bit because we rely on Dryad of the Ilysian Grove pretty heavily which gives us all the subtypes, but it is still powerful in the right shell. You can pick the same land you control 5x with a dryad out, as an example, so it isn't the end of the world. You don't need to destroy 5 separate lands of yours if your opponent doesn't control any as an example.

These are some Fae of Wishes / Wish options that should be considered.

Scapeshift - This is basically the go-to option in most scenarios. It's capable of winning games with Dryad of the Ilysian Grove or Amulet of Vigor + 6 lands out by finding Valakut, the Molten Pinnacle or setting up a (usually) game winning Cultivator Colossus by finding Bouncelands + Tolaria West. With only 5 lands and Amulet of Vigor out, you can run away with the game by transmuting into Primeval Titan in pretty much the same way, depending on which lands you have to sacrifice. It can also function as mana-fixing or ramp depending on the situation as well. Not really the greatest thing in multiples, since most of our lands are important utility lands, but definitely a lot of synergy with the deck overall. It generally ends up a cheaper Cultivator Colossus or Primeval Titan, but sometimes one of your lands in play were important, so it's not always game winning on the spot (we help to mitigate this by running both Hanweir Battlements   + Slayers' Stronghold). It's also pretty horrible without Dryad of the Ilysian Grove or Amulet of Vigor, so it does very poorly against decks with interaction.

Tooth and Nail - Basically a win on the spot card, if you are able to entwine and your opponent doesn't have removal. Eldrazi Displacer + Primeval Titan will let you play all your lands in your deck if you fetch the activation cost for Eldrazi Displacer and use it to blink your titan, to rinse and repeat. Then, you find nothing but value with Mosswort Bridge + Vesuva after attacking (more deck thinning with haste lands). Alternatively, you can find Dryad of the Ilysian Grove + Primeval Titan or just two Primeval Titans to just go for lethal with combat damage and/or Valakut, the Molten Pinnacle. Lots of potential paths all converging to your victory.

Turntimber Symbiosis   - this is basically a creature, or it can be a land. Not a terrible "tutor" for a creature, and it can be sided in quite easily.

Vivien on the Hunt - This is a 1 card combo that gets us to Primeval Titan if we are running Felidar Guardian + Karmic Guide to scale up all of our 3 drops and blink it twice for Primeval Titan. Not the best option, since it requires filling the deck with some suboptimal cards, but it is an interesting option nonetheless.

Esika's Chariot - a nice threat to have, especially if you already have at least 1 Construct 0/0 C from Urza's Saga as they snowball quickly.

Approach of the Second Sun - this is a backup win-con that actually synergizes quite well with the whole wishing plan when you have lots of mana and no real threats (or your opponent has infinite life, etc). Since it goes 7th from the top after casting, and we have quite a few ways to dig through the top of our decks, it can be a rather fast clock (look at the various cards marked with dig in my custom categories).

Biorhythm - a great way to turn around a game, and can even let you win on the spot in the right situation.

Nexus of Fate - Another backup plan card. It's pretty good at buying time, and being an inevitable threat. It also basically hoses mill, while being a relevant alternate win condition in other matches.

Noxious Revival - solid option against targeted discard and mill. Using your graveyard as a second hand against mill, and being able to put Endurance on the top are both backbreaking lines. This is a better on the draw card than Veil of Summer as you won't have the mana for it against a turn 1 Thoughtseize. It's also relevant against reanimator based graveyard decks, but not really a solid form of hate against any other graveyard based decks.

Teferi, Master of Time - this is "creature removal" that can generate value, or just some solid proactive card filtering. There's not really a match I can think of to side him in against, but he is a solid wish target capable of dealing with creatures greater than 5 toughness (one of the few planeswalkers capable of protecting himself).

Lukka, Coppercoat Outcast - a cheeky answer to Blood Moon where you transform your 1 CMC creatures into Dryad of the Ilysian Grove or Primeval Titan in almost every case. Due to layering, Dryad of the Ilysian Grove makes your lands into mountains with all basic land types, so it basically solves Blood Moon.

Blasphemous Act / Firespout - Blasphemous Act is one of the better boardwipes for our purposes, since it gets cheaper as you are more overwhelmed, and is capable of dealing with almost everything. Firespout is a lot more accessible, and is a nice answer to Magus of the Moon as a happy coincidence.

Pithing Needle / Sorcerous Spyglass - quite powerful against planeswalkers, fetches, and anything else with an activated ability. Either option can break certain combo decks if they rely on activated abilities. I generally go with Sorcerous Spyglass because it gives extra information, and can be cast through a Chalice of the Void at 1. However, with Urza's Saga, Pithing Needle can be a better option.

Crucible of Worlds / Ramunap Excavator / Ancient Greenwarden - This is mainly anti-hate, but it also combos nicely with Ghost Quarter or Nurturing Peatland allowing you to set back your opponent with your land plays for the turn or transform your mana into cards, instead of having your extra land plays being strictly ramp. Ancient Greenwarden also doubles triggers when lands ETB, so things like Valakut, the Molten Pinnacle, Crumbling Vestige, Aether Hub, Mosswort Bridge, Amulet of Vigor, and Lotus Cobra all trigger twice (so do all your bouncelands, so be careful about that).

I'm keeping this here more for archival purposes, as I think Fae of Wishes / Wish is almost better in every situation. I ran this wish package for a long time, so I'll just keep this subsection for now.

Silver Bullets

Fracturing Gust - mostly there for affinity/hexproof, or anything else with lots of artifacts/enchantments. I feel the recent Culling Ritual does a better job in most situations, since it can also ramp me. It's basically ramp vs. lifegain when considering the two (instant speed and initial mana cost matters too of course). I tend to think a wipe + threat with the ramped mana is better generally speaking.

Batwing Brume - another form of hate that is fairly specific to certain decks. the mode is potent against the Splinter Twin variants, while the mode is very effective against things like infect that go all in on one turn, where you just need to survive past their combo. This particular silver bullet isn't in my sideboard currently, as I've been seeing a lot less of both types of decks (infinite creature swarms and 1 trick ponies).

Lavinia, Azorius Renegade / Gaddock Teeg / Yasharn, Implacable Earth / Scheming Fence - very strong denial in matches where relevant. Most of the decks Gaddock Teeg shut down have become less prevalent in the meta, so he isn't a needed option right now. Lavinia, Azorius Renegade on the other hand is strong against Tron, and 'free' spells like Solitude, Living End, Memnite, etc. Yasharn, Implacable Earth is very good against fetchlands, and anything that plans to sacrifice anything, like sacrifice outlet creature combo decks, Treasure and Food token decks, etc. Scheming Fence is a solid option against anything with activated abilities. It steals the abilities of anything short of planeswalkers, and it still turns those off. It is like an upgrade to Pithing Needle that's wishable.

Wheel of Sun and Moon - this one is anti-mill and gravehate built into one neat package. It is also a softlock when combined with Elderscale Wurm if your opponent has no form of removal. Simply cast it on yourself and keep casting an instant to prevent yourself from decking out.

Unmoored Ego / Slaughter Games - basically a silver bullet against most combo decks. This lets you completely remove one of their key pieces.

General Options

The Gitrog Monster / Sigarda, Host of Herons / Dragonlord Dromoka / Empyrial Archangel / Hydroid Krasis / Nethroi, Apex of Death / Vhati il-Dal - This slot is basically a multi-colored filler card that's in there for when I just need some presence on the field, but there's lots of great options, even beyond these (I try to go with creatures with at least 1 green cost so they can be found with Summoner's Pact when sided in - being castable with green/white is also suggested, so you always have access to cast it when wished for and aren't manascrewed). The Gitrog Monster is a beater with lots of synergy with the deck. It can transform our excess lands into cards and give us much needed extra land plays every turn. It's only real downside is its lack of protection and evasion. Sigarda, Host of Herons is a hard to remove threat - its effect is notable against annihiliator, plus it's a flyer and hexproof. Dragonlord Dromoka is very good in a lot of matchups, specifically against blue/red due to the uncounterable and lifegain. Empyrial Archangel just ends games where it does its job right. It's biggest downside is that the replacement effect is not optional. Hydroid Krasis is just card advantage and life gain attached to a large beater with evasion and trample. Nethroi, Apex of Death is a different form of anti-removal from the hexproof/shroud options. Let them remove your creatures, then use the mutate cost on this guy to bring back some nice board presence that just happens to be enough to let you use Mosswort Bridge's hideaway. Vhati il-Dal is a very solid controlling option, making my creatures into essentially deathtouch blockers or attackers, or allowing me to block with Vhati il-Dal then tap it before damage calculation and block just about anything without it dying.

There's also a lot of multi-colored planeswalkers, and non-green multi-colored creatures that could be options as well (Geyadrone Dihada / Nicol Bolas, God-Pharaoh / Blood Baron of Vizkopa / Dragonlord Ojutai / Narset, Enlightened Master being some top choices). However, I generally prefer to go with a green creature in this deck, as Summoner's Pact makes a singleton green creature into essentially 5 copies once sided in.

Finally, let's look at some of the more generic removal options - these are some of my top choices:

Potential 2 for 1 or better:
Deafening Clarion
Culling Ritual
Quandrix Command
Crime / Punishment
Hazardous Conditions
Fiery Justice
Maelstrom Pulse
Catch / Release
Razia's Purification

Abrupt Decay
Assassin's Trophy
Vanishing Verse
Anguished Unmaking

Kaya's Guile
Crackling Doom
Hide / Seek
Catch / Release
Riveteers Charm
Eladamri's Call

Honorable Mentions:
Anafenza, the Foremost
Kambal, Consul of Allocation
Knight of Autumn
Meddling Mage
Lightning Helix
Nature's Chant
Detention Sphere
Deputy of Detention

I suggest picking well balanced removal spells for the slots (that fit in your color options, and are capable of dealing with more problems), but the choice(s) is/are yours.

Since Karn, the Great Creator is limited to artifacts, and is the highest CMC of all the wishes, it is probably the worst option of them all. However, it is a permanent, so if the game goes longer, you can get more value from it. It is in a very awkward spot of the mana curve, and most modern games are over by the time it does anything, so I don't particularly like it. However, with that being said, there are some very good options, which are valid sideboard cards with or without Karn, the Great Creator.

Liquimetal Coating - this allows your Karn, the Great Creator to destroy your opponent's lands, provided you can also protect him.

Chalice of the Void - very powerful denial against decks that are efficiently mana-curved, as most modern decks are. This is one that is best played early for 0 or 1, maybe even 2 if facing a hatebears/goodstuff kind of deck. It doesn't deal with any current threats at that CMC, it only prevents future ones from being played. This also hits your own cards as well, so be careful about that. It is findable with Tolaria West, giving it extra value in the deck. If you run lots of 0 or 1 drops, this gets a lot less valuable, as it is a double-edged sword.

Engineered Explosives - targeted CMC removal. Being findable with Tolaria West, gives it extra value in the deck.

Unlicensed Hearse / Relic of Progenitus / Tormod's Crypt - Unlicensed Hearse has better interaction, being twice as powerful, and letting you choose the targets, along with being a potential threat on its own, while Relic of Progenitus is able to cantrip itself, and is findable with Urza's Saga. Tormod's Crypt is a one time shot at 0 CMC, but like Relic of Progenitus, it is findable by Urza's Saga and also Tolaria West making them all have their specific pros and cons.

Pithing Needle / Sorcerous Spyglass - quite powerful against planeswalkers, fetches, and anything else with an activated ability. Either option can break certain combo decks if they rely on activated abilities. I generally go with Sorcerous Spyglass because it gives extra information, and can be cast through a Chalice of the Void at 1. However, with Urza's Saga, Pithing Needle can be a better option.

Haywire Mite - artifact/enchantment removal, something we always want. Also, since this is findable with Urza's Saga it gets some extra value.

The Stone Brain - an effect previously restricted to splashing at least - there's 4+ variations of this effect in multiple colors, but they've always included at least previously - this is a very powerful card. Against a lot of combo decks, eliminating their key card can be back breaking and win the game on the spot.

To make things a little easier, I marked all the cards I sometimes side out in various matches with the tag #flexslot if you look at custom categories.

First of all, when heading into game two, I usually decide what to side out first. I evaluate which cards are less than optimal. Arboreal Grazer gets cut to 1 copy against decks that don't plan to attack much. Things along those lines, where you take out suboptimal cards. Something like Fae of Wishes will almost always go out after the first game, since we are moving most of its relevant targets in (sometimes a flying blocker can be useful).

After all that, I decide which sideboard cards could prove useful in the match, and move them in. Afterwards, I adjust to make my sideboard as close to 15 cards as I can, whether I need to remove more "filler" slots like Summoner's Pact / Eladamri's Call, or if I have to move in some of the "better" cards I tried to side out (dependent on the match).

Another option is removing some utility lands that don't really serve a purpose in the match (Cavern of Souls and Sejiri Steppe) depending on the deck you are facing. I generally don't suggest going down below 28 lands with the deck. Also worth mentioning is don't stress about getting exactly 60/15; there's times I will play with a 61 card deck in game 2 (usually against some weird homebrew where I want more options and lots of our sideboard seems relevant).

Lastly, you can always include some sneaky tech like Hokori, Dust Drinker / Worship / Elderscale Wurm if you have the space (I ran Elderscale Wurm mainboard for a while before modern became a removal heavy format). If you're facing anything with a more aggro build, Hokori, Dust Drinker isn't the best option. For example, puresteel decks can be seen as a combo deck, but they are a more aggro combo deck, where they get early board presence. Hokori, Dust Drinker is not a good option against decks like these, since they can still keep applying pressure even without mana with a quick start, and since a large majority of the meta falls into this aggro-esque category, Hokori, Dust Drinker isn't really poised as a solid sideboard option currently. However, the surprise factor of an obscure card like this definitely pays off sometimes, so that's just something to keep in mind. I am talking about obscure cards in general being a solid enough option if you have the extra slots, and am just Hokori, Dust Drinker as an example. If you feel they will do enough in your meta to justify inclusion, feel free to experiment a little.

Tutor for any 0 CMC
Tolaria West + Simic Growth Chamber

Boseiju, Who Endures + Bounceland

Creature Removal
Arena + Lotus Field
Arena + Sejiri Steppe

Reusable Protection/Unblockable with Sakura-Tribe Scout
Sejiri Steppe + Bounceland

Extra Burn damage with Dryad of the Ilysian Grove and at least 4 lands out
Valakut, the Molten Pinnacle + Hanweir Battlements  for haste (Vesuva can't copy a land entering at the same time, so fetch it after attacking along with the 2nd Valakut, the Molten Pinnacle for 3 copies). You can also target yourself with Ghost Quarter for an extra landfall trigger.

+2/0 and Haste/Vigilance (another fetch after attack)
Slayers' Stronghold + Boros Garrison

Free Plays with 10 power (if you have extra landdrops left, it gets really broken)
Mosswort Bridge + Bounceland - you can stack triggers so you can resolve and activate the hideaway before bouncing Mosswort Bridge back to your hand
Mosswort Bridge + Vesuva allows you to double down on the hideaway almost always (you can't copy the Mosswort Bridge but you will almost always find at least an extra land creature on the first hideaway). This means you can copy a bounce with Vesuva initially, to be able to replay it (now copying Mosswort Bridge) for a second chance at finding a finisher.

Haste without Amulet
Hanweir Battlements  + Crumbling Vestige or a Bounceland and extra land plays to replay the Hanweir Battlements  and give the titan haste

Simic Growth Chamber + Tolaria West - Tolaria West + Simic Growth Chamber lets you transmute into a 0 CMC card
Boseiju, Who Endures + Selesnya Sanctuary - Boseiju, Who Endures + any bounceland lets you have removal for any artifact/enchantment/land
Dryad of the Ilysian Grove + Valakut, the Molten Pinnacle - Valakut, the Molten Pinnacle + Dryad of the Ilysian Grove allows everything to be mountains, so Valakut, the Molten Pinnacle + Hanweir Battlements  becomes one of the better fetch options

If you don't believe something is played out how I described it, please feel free to ask a certified judge here.

Example Hand:
2x Amulet of Vigor
1x Forest or any other untapped source
1x Simic Growth Chamber or any other green bounceland
1x Summoner's Pact / Primeval Titan or in some cases Cultivator Colossus with enough lands in hand
1x Summoner's Pact / Azusa, Lost but Seeking / Arboreal Grazer
2x Dryad of the Ilysian Grove / Wayward Swordtooth

Turn 1: Play an untapped land, then tap it to play Amulet of Vigor.

Turn 2: Tap your first land for another Amulet of Vigor, play a bounceland, untap twice (amulet triggers) and add 4 to mana pool, then bounce that same land back to your hand (unless you have another bounce in hand) so you can use it again.

Turn 2 (continued): Now there's a few variations here, but long story short you need Arboreal Grazer / Azusa, Lost but Seeking or at least 2 other land drop guys (not Sakura-Tribe Scout because no haste) with a Primeval Titan or Summoner's Pact to fetch missing pieces. Cultivator Colossus can work instead of Primeval Titan in some cases as well, allowing you to draw into Primeval Titan or Summoner's Pact with the extra draws and cast it with the extra mana. I'd only go this route if you happen to have 2-3 lands in hand and are feeling lucky.

There's a few ways that you can go about a turn 2 win. First, if you suspect removal (and hopefully have 3 extra mana), you want to play more conservatively and first fetch Simic Growth Chamber + Tolaria West, then transmute the Tolaria West into a Summoner's Pact as an insurance policy against removal (while floating 3 extra mana thanks to your double untaps). After casting your second Primeval Titan with your excess mana, now you go for Boros Garrison + Slayers' Stronghold or Hanweir Battlements  + source to give them both haste. Gruul Turf is probably a decent idea if you used a Summoner's Pact, while Valakut, the Molten Pinnacle is a great option if Dryad of the Ilysian Grove was one of your extra land cards to get to this point. After attacking with both Titans, you'll have 4 land fetches, which will overlap with the other options below.

If you used Dryad of the Ilysian Grove to get this point, you can fetch Valakut, the Molten Pinnacle + Slayers' Stronghold to grant your titan haste, then fetch either Valakut, the Molten Pinnacle + Vesuva or Valakut, the Molten Pinnacle + Mosswort Bridge depending on their blockers and your landcount. If triple Valakut is enough for lethal with your Titan swing, feel free to keep it simple. If that isn't enough, you have to gamble a little bit on the hideaway from Mosswort Bridge getting you there. You can stack triggers so even as you play the hideaway cards, you still have Valakut, the Molten Pinnacle + Mosswort Bridge untapped in your second main.

If you didn't have Dryad of the Ilysian Grove and didn't have the extra mana to play a second titan, your only option is to rely on the sheer power of Mosswort Bridge if you really want to go for that turn 2 win (I'd generally suggest being happy with a turn 3 win and playing more conservatively). You can fetch Boros Garrison + Slayers' Stronghold initially, which after double activating the Stronghold, gets you to 10 power, so you have Mosswort Bridge online. On your fetch, you'd want to find Mosswort Bridge + Vesuva, letting you copy a bounce to return it back to hand to hopefully replay it as Mosswort Bridge when you hit an extra land creature. Basically, from here you need to get lucky enough with the hideaways to keep hitting Primeval Titan / Cultivator Colossus / Dryad of the Ilysian Grove / Azusa, Lost but Seeking / Arboreal Grazer to eventually finish them off with Valakut, the Molten Pinnacle triggers. It's quite possible, but it isn't really something I would rely on, so I'd generally go with a more conservative line that plays around removal.

In the deck's current version, I've cut Sunhome, Fortress of the Legion as it was basically win-more and I was fighting for land slots, so I no longer have that straightforward turn 2 victory available against no blockers (we basically want untapped T1 green sources, and try to limit all other unnecessary lands). There is still the Mosswort Bridge route, and the transmute Tolaria West into two titans route, the Valakut, the Molten Pinnacle route, and the possibility of a turn 2 Cultivator Colossus "drawing" into enough ramp and a way to get at least 1 Primeval Titan out and spiraling from there. The Valakut, the Molten Pinnacle and double Titan routes are fairly consistent when your hand is strong enough for the turn 2 win, so swapping Sunhome, Fortress of the Legion for Mosswort Bridge to cover its aggro use has given the deck a lot more lines of play, alongside more consistency and late game reach (tapped green is generally better than untapped colorless - and we can now dig for specific hate cards far easier). I could theoretically swing with something crazy like Cultivator Colossus + 4 Primeval Titan on turn 2, so we are more than capable of lethal still, there's just some luck involved in some of the paths to get there now. It's a more than fair trade-off though, because I am capable of far more plays with only one amulet out, making turn 3 wins more consistent, which would otherwise be impossib