Seton's Druid Flood
Seton, Krosan Protector is everything I want to be doing in green. He turns every single druid into a mana dork with haste. Since it is his ability tapping them, you can tap a druid for as soon as it hits the table. Outside of two bombs, every creature in this deck is a druid. This turns 1-drops into free cards. It also turns 2-drops into 1-drops, 3-drops into 2-drops, and so on. Throw in a little bit of card-draw, and you have a an engine that can allow turns where you dump half your deck onto the battlefield. Let's look at the pieces.
Mana
Standard Mana Dorks
Arbor Elf, Elvish Mystic, Boreal Druid, Llanowar Elves, and Fyndhorn Elves. These are the classics. Except for Boreal Druid, these let you play Seton on turn 2, which helps set up the engine before most people can interact with it too much.
Heritage Druid and Birchlore Rangers are worse versions of Seton that will give you a little bit of redundancy if someone snipes Seton so you can recast him. They both only work with Elves, but there's a lot of them in this deck.
Slightly Bigger Mana Dorks
Llanowar Tribe, Joraga Treespeaker, and Gyre Sage are a few examples of the other quick ways to get more mana.
Big Mana Druids
Elvish Archdruid and Priest of Titania both can generate a ton of mana when you have dropped a couple elves on the table.
Marwyn, the Nurturer: Again, when you're dropping elves for free, Marwyn can get real big, real quick.
Karametra's Acolyte: Seton, Krosan Protector already generates three devotion by himself, and there are a bunch of other permanents that give you 2 or 3 devotion. She can tap for 10+ mana easily.
Mana Land
Growing Rites of Itlimoc
: You can consistently have 4 creatures out by turn two or three, so flipping this into a Gaea's Cradle is easy.
Wirewood Lodge: Untap Marwyn, Priest of Titania, or Elvish Druid with this one and go even bigger mana.
Then you can use Voyaging Satyr or Krosan Restorer to untap either of these lands and add more gas.
Vernal Bloom doubles the output of your forests.
Going Off
Cost Reduction
Rhonas's Monument and Emerald Medallion will let you also play your druids for free.
Card Draw
Glimpse of Nature is the best green card-draw spell that exists. Play it on the turn you think you can go off, and let every creature you play replace itself.
Guardian Project and Beast Whisperer: Get either of these on the battlefield the same turn you play glimpse, and each creature you play draws you two cards. Gilt-Leaf Archdruid does the same for every druid you play.
Shamanic Revelation: If you start to run out of new creatures to play, but still have a ton of mana, this draws you a bunch. This works great on turn three when you have 4 or 5 creatures out, but it can win you the game one turn five or six when you have 10+ creatures out.
Lifecrafter's Bestiary: The scrying is nice, but it can also function as a more expensive glimpse.
Voice of Many: You will almost always have the most creatures out. This is like a Harmonize that also puts a 3/3 mana dork onto the table.
Nantuko Cultivator: This card is especially great if you've drawn a bunch off of your other draw spells and want to replace all the dead land in your hand with more card draw. The +1/+1 counters are nice too.
Untapping
Have you dropped 20 creatures onto the table but now they are all tapped out? No worries.
Mobilize, Vitalize, and Benefactor's Draught will untap your creatures if you need more mana from them, or if you're ready to try and overrun. Benefactor's Draught has the added utility of playing when an opponent is attacking another opponent who has a lot of creatures out if you want to draw some cards.
Quest for Renewal lets you easily untap your creatures on your opponents upkeeps, so you aren't too defenseless if you end up whiffing when you try to go off.
Even More Druids
So you have 10+ creatures out, and more mana than you know what to do with. Time to take it to the next level.
Kindred Summons, naming druid lets you double to number of druids you have on the board for only 7 mana. Genesis Wave for a bunch or play Primal Surge to empty even more of your deck onto the board. There are only 10 instants or sorceries in the deck, so you will likely hit 5+ permanents off of Primal Surge.
Winning
I've included a number of unconventional wincons, because Magic is more fun that way! But we will start with the traditional green wincon...
Overrun
Door of Destinies does serious work. Easy to get 6 or 7 charge counters on this and buff your board.
Beastmaster Ascension also gets seven quest counters really easily and helps buff your guys.
If you have too many cards in hand, Jolrael, Mwonvuli Recluse can take advantage of that and make your creatures as strong as your hand size.
Baru, Fist of Krosa and Earthshaker Giant are both druids who help give your attackers trample. But Kamahl, Fist of Krosa is the real workhorse, letting you pump a bunch of mana into powering your attackers.
Other Ways of Winning
Aetherflux Reservoir is a broken magic card. Play 10 spells in a turn and you've generated enough mana to snipe another player. But this deck can play a lot more than 10 spells in one turn. Even if you start your turn at 1 life and have three opponents each at 50 life, if you can play 17 spells in a turn, you've generated enough life to take out everyone in one turn. 17 spells sounds like a lot, but with a card draw engine on and one well timed untap spell, it is very possible.
You would be hard-pressed to find a deck that is a better fit for Throne of the God-Pharaoh than this one. This will drain other player's health quickly enough it can sometimes win on its own, but even if it gets dealt with, it makes overrunning that much easier.
Other Cool Synergies
To be completely honest, half the reason I wanted to build this deck was to pull off Gilt-Leaf Archdruid's land control ability. Get 14 druids on the table, play Mobilize, tap all of your druids to steal the lands of two players? Use their mana to get more druids on the table to take all the lands of the whole table? Beautiful.
Harvest Season has some really interesting interactions with this deck. Play while Baru, Fist of Krosa and a dozen tapped druids are on the table and you've suddenly given your creatures +13/+13. Play it after dropping an Avenger of Zendikar to make your plant tokens terrifyingly strong. Genesis Wave and Primal Surge also usually hit a ton of lands and have a similar effect. Grab your 12 tapped forests with Harvest Season and then sacrifice Llanowar Druid to untap them all.
Kamahl, Fist of Krosa + Sylvan Advocate
lets you pay to turn forests into 3/3 creatures.
There's also a lot of +1/+1 counter interactions that are going on here. Citanul Druid, Gyre Sage, Nantuko Cultivator, Marwyn, the Nurturer, Bane of Progress, Incubation Druid, and Oran-Rief, the Vastwood all generate +1/+1 tokens. You can then play Slippery Bogbonder to move all those tokens onto a hexproof creature if you're feeling Voltron.
Interaction
This deck is mostly focused on trying to do things too quickly for others to stop, but if anyone is trying to slow things down, there are a couple of ways to deal with that.
Nullmage Advocate, Druid Lyrist, Krosan Grip, Freyalise, Llanowar's Fury, and Bane of Progress let you deal with artifacts and enchantments.
Green is notoriously bad at dealing with other creatures, but we do run a copy of Lignify that we can grab with Treefolk Harbinger if we need to.
