msem-instigator

Whenever a land you control enters, create a 1/1 red Elemental creature token. Then if you control three or more Elementals, exile Aleryn, Trapseeker, then return him to the battlefield transformed under his owner's control.

Menace
At the beginning of your upkeep, put a prize counter on target permanent you don't control.
Whenever a permanent with a prize counter on it is put into a graveyard from the battlefield, return it to the battlefield under your control.

Menace
Whenever a creature blocks, put a -1/-1 counter on that creature at end of combat.
Creatures with -1/-1 counters on them can't block.

Menace
Whenever Algrin's Legacy becomes the target of a spell an opponent controls, that spell's controller loses 5 life unless they discard a card.

Lethal damage dealt to creatures is determined by their power rather than their toughness.

When Allagras' Vanguard enters, create two 1/1 blue Merfolk creature tokens with “When this creature dies, draw a card, then discard a card”.

Alluring Rider must be blocked if able.
Attain {4}{G} ({4}{G}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

When Almgrove Performer enters, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — You gain 3 life.

Flying, lifelink
Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
You may cast this card from your graveyard as long as you're in a renaissance.

Alquyut Mount can't attack or block alone.

Whenever Alrathan Scholar deals combat damage to a player or planeswalker, draw a card.
{2}{U}: Target creature gains flying until end of turn.

Flying, prowess
Whenever an artifact you control enters, you may draw a card. If you do, discard a card.

Motivate 2 (When this creature enters, you may motivate target creature with less power than this by putting two +1/+1 counters on it.)
{1}{W}: Target creature with a +1/+1 counter on it gains lifelink until end of turn.

First mate—At least half the cards in your starting deck are lands. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
Trample
{1}, Discard a land card: Put a +1/+1 counter on Alvarez. He deals 1 damage to any target.

Trample
Each creature you control with a counter on it has trample.

Reach
When Ambush Predator enters, you may return target Horror creature card from your graveyard to your hand.
When Ambush Predator dies, exile it and create a 3/2 green Horror creature token.

Flash (You may cast this spell any time you could cast an instant.)
Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Trample
As long as it's an opponent's turn, Ambushing Alligator is a blue Bird with base power and toughness 1/1 and has flying and hexproof.

When Aminatou's Adherent enters, judge target creature you control. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)
Whenever you condemn a creature, creatures you control gain menace until end of turn.

Reach, vigilance
When Amorphous Tyrant enters, another target creature you control deals damage equal to its power to target creature or planeswalker you don't control.
Evoke {G} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Flash
When Ancestral Warlord enters, it deals 1 damage to each blocking creature.

Whenever Ancient Durumderm attacks, you may return another creature you control to its owner's hand. If you do, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Ward {2}
When Ancient of Lotus Lake enters, draw a card.

When Andazir Veteran enters, amass Soldiers 2. (Put two +1/+1 counters on an Army you control. It's also a Soldier. If you don't control one, create an 0/0 black Soldier Army creature token first.)

At the beginning of each end step, if you drew and/or discarded six or more cards this turn, return Anemothrys, Reefcrown from your graveyard to the battlefield.
Cycling {R}{G} ({R}{G}, Discard this card: Draw a card.)