msem-instigator

[+1]: Create a 1/1 green Merfolk creature token.
[0]: Target artifact or creature loses all abilities and becomes a green Seal creature with base power and toughness 3/3.
[–6]: Up to five target noncreature permanents lose all abilities and become green Merfolk creatures with base power and toughness 1/1.

Alpha (You may have this creature enter with a +1/+1 counter on it. If you do, it becomes alpha and can only attack alone.)
Vigilance, reach, trample
{4}{G}{G}, Exile Qiyan, Serpent of Seven Heads from your graveyard: Create seven 1/1 green Snake creature tokens. Activate only as a sorcery.

Trample
Whenever Quakestep Behemoth or another creature you control enters, put X +1/+1 counters on each creature you control, where X is the entering creature's power.

Whenever Reclamation Grovesculptor enters or attacks, put a growth counter on target noncreature permanent. It becomes a colorless Forest land and loses all other card types and land types.

Destroy target noncreature permanent. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

{G}: Exile target card from a graveyard. If it was a land card, put a +1/+1 counter on Sacrificial Bull.
{G}, Sacrifice Sacrificial Bull: You gain life equal to its power.

Trample
When Scion of Flourishing enters, put a +1/+1 counter on each other creature you control. Those creatures gain trample until end of turn.
Whenever a Forest you control enters, you may aetherize Scion of Flourishing. (To aetherize, create a token that's a copy of it, then exile that token.)

Concord — {1}{G}: Until end of turn, Seadrake Rider gets +2/+3 and must be blocked if able. Activate only during your turn, only once each turn, and only if there are four or more card types among permanents you control.

As long as you control four or more lands, Seeker of Untouched Beauty gets +2/+2 and has trample.
When Seeker of Untouched Beauty dies, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Pressure {2}{G}{G} (You may cast this spell for its pressure cost if there are seven or more cards in your graveyard.)
Trample, hexproof
Shambling Dreadreef's power and toughness are each equal to the total number of land cards you own on the battlefield and in your graveyard.

Haste
Whenever a creature attacks, Slashing Pangolin gets +1/+1 until end of turn.

Enchant land
Whenever enchanted land is tapped for mana, its controller adds {G}.
{G}, Sacrifice Sleeping Dryads: Draw a card.

Chosen one ({W}{U}{B}{R}{G}: Transform this permanent.)
When Sower of Wishes enters, reveal the top three cards of your library. Put all land cards revealed this way into your hand and the rest back on top in any order.

Flying
At the beginning of your first main phase, you may put any number of land cards from your hand onto the battlefield, then draw a card for each land put onto the battlefield this way.

Reveal cards from the top of your library until you reveal a land card, then put that card onto the battlefield tapped. You may put another card revealed this way on top of your library. Put the rest of the cards revealed this way on the bottom in a random order.

You gain 7 life.
Coalesce {5}{G}{G} (You may cast this from your graveyard for {5}{G}{G}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

{T}: Add one mana of any type that a land you control could produce.
Augmented — At the beginning of your end step, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, untap Thriving Budling and put three +1/+1 counters on it.

Trample, haste
Thriving Hydra enters with four +1/+1 counters on it.
When Thriving Hydra enters, for each other creature you control, put X +1/+1 counters on that creature, where X is four minus its power.
Whenever Thriving Hydra attacks, double the number of +1/+1 counters on each creature you control.

Search your library for a land card, put it onto the battlefield tapped, then shuffle.
Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, untap that land.

Flash
When Tsang Jin, Master of the Jade Sea enters, put target land card from a graveyard onto the battlefield under your control.

Whenever you cast a nongreen spell, creatures you control get +1/+1 until end of turn.
Wanderlust — When Untethered Disciple enters, if you control four or more differently named lands, create two 1/1 Scout creature tokens that are all colors.

War-Pride Champion can't be blocked by creatures with power 2 or less.
Stampede — Whenever War-Pride Champion and a creature with greater power attack, target creature you control gets +2/+2 until end of turn.

When Weald Sentry enters, search your library for a basic land card, reveal it, put it into your hand, then shuffle.
When Weald Sentry dies, draw a card.

As an additional cost to cast this spell, sacrifice a creature.
Search your library, hand, or graveyard for a creature card with mana value 1 greater than the sacrificed creature's and put it onto the battlefield. If you searched your library this way, shuffle.

Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Whenever Wild Lifescale attacks, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)