Here I'll discuss why I think each card deserves a spot in the 99.
Commander
Meren of Clan Nel Toth is the perfect commander for a deck that focuses around attrition and graveyard shenanigans. This Jund necromancer provides pure value to you and if built correctly, can truly cripple your opponents ability to react. While Meren is on the field, at the end of turn, you target a creature card in your graveyard. If this creature card has a converted mana cost (cmc) more than the amount of experience counters you currently have, the card is returned to your hand. However, if the card has a cmc of equal to or less than the amount of experience counters we have, the creature goes straight to the battlefield. Now 'how do we gain these counters?' you might ask, well that's quite simple. When a creature you control dies and Meren of Clan Nel Toth is on the board, you get an experience counter. Easy to understand but extremely powerful. Therefore our goal is to gain value through the act of sacrificing our own creatures and gaining value off of ETB effects and the fact that it's quite hard for our opponents to completely remove a creature.
Card Draw
Card draw is quite important in magic as it allows us to find the answer to threats quicker than the threat can occur. The more cards you have at your disposal the more answers you will have to an immediate threat on the board. Our card draw package utilizes the death of creatures as Meren draws her power from the death and suffering of them.
Deathreap Ritual: Things are guaranteed to be dying all the time. Deathreap Ritual will draw you ALOT of cards.
Disciple of Bolas: Lets you sac something, gain life and draw cards. Disciple of Bolas is always good in a Black deck that wants things to die.
Grim Haruspex: Things are always dying in your deck, it's like a lesser version of Deathreap Ritual that can be brought back easily with Meren. Don't under estimate this card. Also, in this deck we never use its Morph ability.
Grisly Salvage: Chucks a bunch of things into the graveyard and technically lets you tutor the top 5 cards for a creature or land card. Generally you'll grab a land as you can just get the creature back from the grave with Meren.
Skullclamp: Things are constantly dying in this deck so you'll always be drawing cards. The deck also produces tokens which will let you draw cards off of them and sacrifice them.
Vulturous Aven: It's an Altar's Reap on a creature, Meren cares about creatures so it's more worthwhile to run effects on creatures as opposed to instants and sorceries. Lets you draw 2 cards and lose 2 life for the small cost of sacrificing a creature (generally a token). Note, it can exploit itself.
Lands
Our mana base is a no brainer when it comes to wanting to play the game. It's also one of the hardest aspects to fine tune and tends to take alot of time. I've tuned it to the best of my ability currently and it's fairly consistent as long as I get an early Green source. The lands will provide us with the ability to cast what we want while also having some utility factors such as making our commander alittle cheaper when she gets too expensive or by blowing up another reanimators graveyard.
Blooming Marsh: First two turns this comes out as an unfetchable Bayou. Have you seen how expensive Bayou is? Blooming Marsh is an amazing card for any decks running Golgari. After 2 lands are on the field it's just a Guildgate... that's still not too bad considering it has the potential to be a BAYOU!
Bojuka Bog: Sometimes you just need to nuke an opponents graveyard. Don't want any other pesky graveyard shenanigans going on, that's your job.
Command Beacon: Meren being a core piece in this grindy engine, sometimes she just gets alittle too expensive to cast from the command zone. No fear, Command Beacon is here. Playing Meren from the hand is a great alternative late game when she's expensive.
Command Tower: It's an unfetchable Bayou. Staple in any deck running 2 colours or more.
Evolving Wilds: Evolving Wilds just helps us get the type of basic land we need. Early game (before we get our Dawntreader Elks and Sakura-Tribe Elders going) we're really hurting for the correct colours of mana so Evolving Wilds helps.
Forest: I don't think I need to explain this.
Golgari Guildgate: Just your typical land that taps for G or B. Only downside is it comes in tapped.
Hissing Quagmire: A pet favourite of mine since it was released. I don't use the manland ability often but it's nice to have another dual land.
Jungle Hollow: Golgari Guildgate that gains you a life when it enters, solid.
Llanowar Wastes: It's sort of like an Overgrown Tomb that keeps shocking you that can also be used as a colourless source.
Mana Confluence: Mana fixing at the cost of 1 life. We tend to feel strained on Forests early game so this helps alot.
Nykthos, Shrine to Nyx: Tapping for colourless is nice. The devotion ability is used towards the end game when you have big creatures/enchantments out like Sheoldred or Gravepact granting you alot of mana.
Overgrown Tomb: Shockland. Always good to have and can be fetched by Windswept Heath and Wood Elves. It's basically a balanced Bayou.
Swamp: I don't think I need to explain this either.
Tainted Wood: After a turn or two we almost always have a swamp on the field. This is a great mana fixer.
Temple of Malady: Free scry is always nice to set up our next play.
Temple of the False God: Colourless ramp later in the game. Sort of like a Sol Ring on a land when we hit 5 lands.
Urborg, Tomb of Yawgmoth: Fixes our black mana. Brutal with Cabal Coffers, Magus of the Coffers and friends.
Windswept Heath: I'm generally against off coloured fetchlands in EDH but I'm giving this the exception until I can get my hands on a Verdant Catacombs (It's crazy expensive) as I'm always in need of Forests.
Woodland Cemetery: It's the reverse version of Blooming Marsh and you can see how much I like Blooming Marsh so Woodland Cemetery is no exception either. BAYOU!
Ramp Package
We're not going to be able to cast our big menacing spells without mana. Our ramp package will provide us with early game acceleration in both mana base as well as experience counters for Meren. Our ramp package also provides us with late game cheap creatures to feed to our Dread Return effects and Smokestack effects.
Dawntreader Elk: Sac the Elk, gain a land, gain a counter. A very good card to loop early game. Similarly alot of cards in my ramp package are great early game to accelerate both my mana base and my experience counters.
Elvish Mystic: I feel this is a better version of Elves of Deep Shadow for the soul purpose that Green is alot more important early game. However I might consider replacing Elvish Mystic with Elves of Deep Shadow if Black mana in the early game begins to be a major issue. Another plus is thatElvish Mystic enables an earlier Meren and can be sacrificed to Skullclamp.
Farhaven Elf: The little brother of Dawntreader Elk and Sakura-Tribe Elder. Great card to increase your land drops and a good Meren target early game.
Golgari Signet: Signets are great ways to both ramp in EDH as well as fix your mana so it's quite justified to run them.
Magus of the Coffers: Cabal Coffers on a body. I'd much rather run Cabal Coffers but I don't have the cash for it right now. Magus of the Coffers allows for a large amount of black mana to be generated especially in conjunction with Urborg, Tomb of Yawgmoth.
Oracle of Mul Daya: Don't underestimate her power. The Oracle lets you almost always get your land drops, lets you accelerate your land drops and lets you see your next draw. The amount of card advantage she provides is phenomenal. If you've ever played her you'll know what I'm talking about here. Always a welcomed card if you need the added ramp.
Sakura-Tribe Elder: Similarly to Dawntreader Elk, this little snake ramps like crazy but is even better. Being able to loop Sakura-Tribe Elder at the start of a game is a really strong early game strategy.
Sol Ring: Turn 1 Sol Ring is a staple Turn 1 play in EDH. Sol Ring is an immensely powerful card and a must run in almost every EDH deck. Most notable play is getting Meren out Turn 2.
Wood Elves: A bigger brother to the other Land fetchers I run. Lets me fetch any forest in my deck (crucial for Meren) this includes any OG Duals or Shocklands.
Recursion
Our strategy revolves around the graveyard but we can't rely on just our commander to help bring back creatures. We need a suite of recursion to provide more value from the grave to continuously pummel our opponents.
Animate Dead: Lets you cheaply get a creature back from the graveyard. There's no downside to it either.
Dread Return: Unconditional reanimation that we can flashback later in the game by simply sacrificing some creatures (Did I mention this deck loves to sacrifice creatures for value?). Dread Return is a must have in a Meren deck, especially if you run token generators as Dread Return has virtually no downside.
Eternal Witness: Meren likes abilities on creatures as she can easily get them back from the grave. However, we can't run all our effects on creatures nor can we 100% rely on Meren being on the board so we have to run some Instants and Sorceries. Eternal Witness allows us to get these Instants and Sorceries back to reuse again. She also lets us get back other important key cards such as Gravepact effects and Enchantments. She can fetch a land that we chucked to the grave because of Grisly Salvage and she can get back a creature if we just need a creature for the scenario. Honestly she's a staple in any deck that wants to run Green.
Hell's Caretaker: Lets us reanimate a creature at the beginning of our turn. Reanimation effect is also on a creature so we'll be gaining alot of value and versatility out of him. The only downside is that you have to use his effect at the start of turn. Oh and did I mention that he can actually sacrifice to himself to recur stuff?
Liliana, Heretical Healer
: Liliana is an absolute monster in this deck and there's alot of factors I'll need to cover to get this point across. Firstly, she's a creature to start off with and Meren adores creatures being in her graveyard. Therefore Liliana is a very easy card to get back to the field especially due to her low cmc. Secondly, the way she flips to her Planeswalker side is hilariously easy (Have I mentioned that Meren loves things dying?). Once you flip her with easy you gain a 2/2 zombie which you can easily just use as sacrifice fodder or a nifty little attacker. Her first ability (+2) is one sided, every chucks a card into the graveyard. But you don't care about cards going to the graveyard, that's just a second hand to you because of all your reanimation effects. Her second ability (-X) allows you to reanimate any non-legendary creature that you have in your graveyard. Just another big stupid reanimation effect that can grab almost any creature is just great. Her third ability (-8) is potentially game winning in almost every deck, especially this one. You see, we want things to be constantly dying and once she has this emblem, every time something dies it just comes back to the field under our control. Now we run alot of destruction effects such as removal, gravepacts and stax effects so we'll be constantly forcing our opponents to sacrifice things (which will in turn come back under our control). I just cannot stress enough how great of a card Liliana, Heretical Healer is in this deck.
Mikaeus, the Unhallowed: Mikaeus makes all my sac outlets that much more valuable and makes my creatures that much harder to be removed as they just keep coming back. Boardwipe? Not an issue here. Mikaeus can also enable valuable combos in a Meren deck such as with a Woodfall Primus or Puppeteer Clique and lets not forget himself and Triskelion.
Sheoldred, Whispering One: Aside from Sheoldred being a big stupid beater she also comes with very relevant abilities that Meren will absolute love. Her first ability is basically the same ability as Meren has but at the start of your turn instead of the end 'Return target creature from your graveyard to the battlefield', but this doesn't care about the cmc of the creature card so you can get back whatever you'd like. Her second ability allows her to work against our opponents and keep doing what this deck loves to do: forcing our opponents to not have creatures. Sheoldred is a very powerful creature and a great addition to this deck.
Victimize: Victimize is sort of like Dread Return's Flashback effect but on steroids
Removal Package
We're not going to be able to tackle our own strategy if we have opponents threatening us with powerful creatures, artifacts and enchantments so we need ways to remove these threats so that we can become the threat. Removal is essential in EDH as it allows you to go amount your gameplan without the roadblock that would be other opponents. Removal also provides us with alot of politics as we can bargain with other players to not remove threats or we can help people out by saving them from a massive smack to the face.
Acidic Slime: Acidic Slime provides us with a creature that comes equipped with an artifact, enchantment or land removal package. His Deathtouch is also quite relevant as opponents will not want to trade their creatures with him as he'll just come back and blow something up.
Beast Within: One of the best Green removal cards in the game. It allows us to destroy any permanent at instant speed. The opponent gets a 3/3 but that isn't too much of an issue as it's bound to die from a variety of cards in this deck.
Caustic Caterpillar: This little artifact and enchantment eating caterpillar provides us with a way to remove artifacts and enchantments as well as gain experience counters early game. Late game, Caustic Caterpillar provides us with a Gravepact trigger as well as sacrifice fodder for other cards.
Deathrite Shaman: Our 1 cmc planeswalker of the deck. Deathrite Shaman provides ramp, life drain, life gain and graveyard hate. He's a valuable utility creature in any GB/GBx deck and should not be overlooked.
Decree of Pain: A great boardwipe that can draw us a large amount of cards. It also has the added benefit of being able to wipe a board of tokens and small creatures for cheap while also netting us 1 card.
Fleshbag Marauder: This guy will have us forcing our opponents to sacrifice a creature. He helps us get around Hexproof and Shroud creatures while also kicking a Voltron players ass. Generally you'll be casting him and sacrificing himself to the trigger netting you an experience counter and only the opponent at a loss.
Gaze of Granite: The sorcery version of Pernicious Deed a very powerful removal card. While Gaze of Granite doesn't apply the same amount of pressure that Pernicious Deed does, it allows us to surprise our opponents with a controllable boardwipe.
Ghost Quarter: I feel that it is a necessity to run atleast one land removal card in EDH. I run a few but this one is solely for land removal. Gets rid of pesky of a Gaea's Cradle or a Cabal Coffers. I'm looking into picking up a copy of Strip Mine or a Wasteland. While Strip Mine is obviously the better option here, I have a bias towards Wasteland, even if it doesn't hit Basics (Which I'm okay with because I'm not that competitive).
Krosan Grip: Uncounterable, Instant Speed Artifact and Enchantment removal is so valuable in EDH. It would be silly not to run Krosan Grip if you have access to Green. I've also considered Abrupt Decay as it hits more although it's conditional due to the CMC factor. I've seen alot of GBx competitive lists running it so I might keep mine as more of a Sideboard card. For now Krosan Grip can hit bigger things.
Maelstrom Pulse: Has the ability to hit every nonland permanent type. Occasionally Maelstrom Pulse can wipe a board of tokens OR all Sol Rings in play. I consider it an undoubtedly better version of Putrefy aside from its Sorcery speed status.
Manglehorn: Another piece of removal aimed at artifacts. It also comes with the added benefit of completely shutting down artifact strategies which is a great stax bonus.
Massacre Wurm: Provides us with a mini boardwipe on ETB and can potentially drain our opponents for alot over the course of the game.
Merciless Executioner: Exact same utility as Fleshbag Marauder.
Shriekmaw: Rule of thumb is to never hardcast him. Only ever Evoke him and treat him as a Doom Blade. Shriekmaw provides us with cheap removal and a cheap way of gaining experience counters.
Terastodon: Remember how I said that Beast Within was the best removal Green has? Well welcome to this big stupid elephant that comes equipped with 3 Beast Withins that can't target creatures but can target virtually everything else. He can truly cripple your opponents strategy by blowing up key artifacts and enchantments while also slowing them down by completely nuking their mana base. A fun strategy would be to loop him a few times with Meren then cast a boardwipe leaving your opponents with nothing, not even lands. If blowing shit up isn't your style you're still going to be getting a massive 9/9 to smash into your opponents faces. I love this big stupid elephant.
Toxic Deluge: A cheap boardwipe that can remove indestructible creatures for the low low price of your life. In commander you start with 40 life, life loss isn't too much of an issue in a 40 life format when you're able to remove all creatures.
Sacrifice Outlets
Creatures dying plays an important role in a Meren deck however we can't always rely on our opponents destroying our creatures so we must look towards other methods of sending them to the grave.
Ashnod's Altar: Provides us with a way to sacrifice our creatures (especially our tokens) for cheap ramp.
Evolutionary Leap: It's sort of like a really balanced, randomized Survival of the Fittest. Lets us sacrifice a creature and take cards off of the top of our library till we hit a creature and draw that card. Fun fact, most of the creatures in the deck provide so much value that it doesn't matter what creature we hit.
Grim Backwoods: Just another sacrifice outlet that lets us draw a card when the creature is sacrificed.
High Market: Great free sacrifice outlet on a land that gains us a life.
Viscera Seer: One of our better sacrifice outlets in the deck, allowing us to semi-control what cards get drawn next. He's also incredibly cheap so you can get him down early and start the Meren engine rolling.
Stax Package
Stax is a way of locking down the board and basically forcing your opponents to not play Magic. Meren works very well as a Stax commander as she makes alot of the keycards in a Stax list very one sided. Say you have your Smokestack on the field (Stax being named after Smokestack), and you have 1 soot counter on it. On each of your opponents turns they'll be forced to sacrifice a permanent, when it gets to your turn, you simply sacrifice one of your many tokens or any creature for that matter (and gain a counter from Meren ofcourse). End of turn Meren's ability triggers and you bring back said creature to the battlefield. Your opponents don't have this versatility, they're getting hurt and you're gaining value. That's what stax is and that's why Meren is absolutely brutal in this field.
Archfiend of Depravity: Archfiend of Depravity absolutely demolishes creature strategies and reduces the amount of creatures opponents can decide on when I force them to sacrifice things by way of Merciless Executioner. He's also a decent body on a flier which is a plus.
Dictate of Erebos: See Grave Pact below
Grave Pact: You have things dying constantly while gaining benefit and Grave Pact forces your opponents to sacrifice things without any benefit. Opponents generally can't risk removing or blocking one of your creatures in the fear that they might have to remove their own. It's a beautiful thing when you cast a Fleshbag Marauder sacrificing itself and forcing your opponents to sacrifice 2 creatures.
Smokestack: I wish I could run Braids, Cabal Minion over this. Smokestack lets me lock down the field and control how much can stick around. Gone unanswered this can be brutal. Meren can withstand it due to her ability as well as our supply of token generators.
Void Winnower: This slows the board to a grinding halt. There's a surprising amount of cards with even CMC and Void Winnower absolutely HURTS. In theory Void Winnower stops half of the cards in magic and alot of the cards that would be able to remove it. Void Winnower really forces your opponent into a corner minimizing what they're able to do.
Tokens
Tokens play a big role in my deck. They're one of the key cards that I abuse death triggers with. They provide me cheap counters for Meren, cheap activations of Gravepact, some ramp by way of the Eldrazi Scions, blockers and fodder for Smokestack. Cards such as Avenger of Zendikar, Grave Titan and Wurmcoil Engine are here to provide me with the value I stated above while also pressuring my opponents for a win. Tokens in alot of Meren decks are very valuable.
Avenger of Zendikar: EDH is a game of large land counts. When Avenger of Zendikar drops you're going to generate a large supply of tokens. Given, they're only 0/1's but they'll be primarily used as sacrifice fodder. However, say you now drop a land, you have an army of 1/1's that will keep getting bigger the more lands that come into play under your control. Avenger of Zendikar can potentially be a game finisher.
Awakening Zone: On each of your upkeeps Awakening Zone spits out a 0/1 token with the ability to sacrifice itself and generate us some colourless mana. This simple 0/1 on each of our upkeeps provides us with a way to quickly increase our experience counters while also slightly putting us ahead of the curve in terms of mana quantities. Awakening Zone proves even more brutal when we have a Gravepact effect in play allowing us to force our opponents to sacrifice a creature each upkeep.
Creakwood Liege: Creakwood Liege procides us with a 1/1 black and green token on each of our upkeeps. However he also provides +1/+1 to our black creatures and +1/+1 to our green creatures. While he's on the board he's pumping out 3/3's while also buffing our entire team. We can use his tokens as sacrifice fodder or we can use them to swing for the kill.
From Beyond: Similarly to Awakening Zone, From Beyond spits out tokens however they come out as 1/1's so while they provide the same versatility as the Awakening Zone tokens, they can also be used to swing at your opponents. From Beyond also has another clause in its ability where you can sacrifice the token generator itself and search your deck for an Eldrazi and put it into your hand. We only run 1 Eldrazi in this deck and it's Void Winnower. If you read the card write up in the stax section you would know how brutal Void Winnower is to our opponents so the ability to search it up with From Beyond is another big benefit.
Grave Titan: "Death in form and function". This guy spits out 2/2 Zombies like crazy and himself alone can be a win condition. You're able to attack with a horde of Zombies each turn or abuse his ETB trigger with Meren to generate an absurd amount of 2/2s. This guy alone is a heavy hitter at 6/6. He's a creature I almost always include in decks that run Black.
Wurmcoil Engine: He is indeed an engine. A value engine. The deathtouch makes him scary to block or attack into and the lifelink helps with other life draining aspects of this deck. You're also able to sacrifice him for his tokens and then bring him back end of turn. Rinse and repeat for an army of scary steel clad wurms.
Tutors
Tutor cards make the deck run more consistently. EDH is a format that loves the random nature of an 100 card singleton format but sometimes you just need to give a deck the added kick. These cards provide that consistency and gain me valuable plays.
Crop Rotation: We run so many great utility lands that Crop Rotation is a no brainer! Graveyard deck giving you troubles? Bojuka Bog to the face! Need to remove a pesky Gaea's Cradle? Ghost Quarter/Strip Mine/Wasteland. Need that extra kick of mana? Cabal Coffers.
Dark Petition: A nice tutor that is technically cheaper if you have spell mastery. I'd rather a Demonic Tutor or Vampiric Tutor but I'm not complaining, Dark Petition will eventually be replaced by them anyway.
Dimir House Guard: This guy pulls so much weight. Our 4 drop slots are filled with high powered cards so transmuting for them is exceptional. On the field he acts as another sacrifice outlet for us and is also generally unblockable.
Eldritch Evolution: It's a one time Birthing Pod that can search for any card with cmc equal to or less than the sacrificed creatures cmc + 2. Need I say more? Birthing Pod would also be good in this position and far more abusable but I personally like Eldritch Evolution
Entomb: Turn 1: Swamp, Entomb Sheoldred, Whispering One. Turn 2: Animate Dead Sheoldred Whispering One. Entomb is a very good tutor in a graveyard based deck and especially in Meren where it can easily fetch you the option you need to fight back.
Fauna Shaman: A Survival of the Fittest on a creature. If you've ever used Survival of the Fittest in a graveyard deck you'd know that this card is bonkers. While I can't afford Survival, I can afford his little sister Fauna Shaman. Fauna Shaman is a more balanced version of Survival of the Fittest (which is on the Reserved List). Just drew a creature card that you didn't really want? Discard it and find the one you wanted but reanimate the discarded card at the end of turn with Meren. Rinse and repeat.
Jarad's Orders: A mix between a Demonic Tutor and an Entomb, very good card in Meren.
Sidisi, Undead Vizier: A tutor on a creatures ETB is always good. A tutor on a creatures ETB that can sacrifice itself in a deck that brings back creatures from the graveyard is ridiculously powerful. You can loop Sidisi and search out all the necessary cards you need. She's a must include in any deck that runs black and wants things dying.
Value Cards
Value cards are cards that do not fit in any other of the above categories yet still play important roles in Meren's Graveyard. These cards provide control and advantage against my opponents and Gray Merchant of Asphodel provides me another wincon in the deck.
Gray Merchant of Asphodel: This guy drops as a massive bomb always. Just with Gary on the board you're already draining 2 from each opponent and generally gaining yourself 6. Add Meren to the mix to repeatably sac and resurrect him and you have a crippling life loss to your opponents. In this deck the top of our curve gives us alot of devotion (Gravepact, Mikaeus, Sheoldred) so Gary ends up hitting harder than Kokusho, the Evening Star. Gary provides a swift wincon if not dealth with.
Lightning Greaves: These are in here as a way to protect Meren (and by extension, cards like Sheoldred). She's a crucial piece in pushing this deck overboard in terms of value and we want her on the board as long as possible.
Spore Frog: This little guy is an absolute powerhouse in a Meren deck. Constantly being able to sacrifice him and giving you protection from damage during a turn and then bringing him back at the end via Meren is extremely abusable.
Westvale Abbey
: Sometimes you need to tap for colourless mana, sometimes you need to throw out a 1/1 to keep your Smokestack engine going, sometimes you want to hit your opponent with a 9/7 Flying, Lifelink, Indestructible, Haste Demon called Ormendahl, Profine Prince.
