msem-instigator

When Affluent Knight enters the battlefield, recruit, then recruit again. (To recruit, create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)

When Aftermath of the Surge enters the battlefield, create two Treasure tokens.
{1}{U}, Sacrifice two artifacts: Draw two cards.
{3}{U}, Sacrifice four artifacts: Create an 8/8 blue Kraken creature token. It can't block this turn.

Flying
When Ageless Lorekeeper enters the battlefield, you may discard your hand. When you do, draw three cards.

When Ageless Weaver enters the battlefield, create a green Aura enchantment token named Years of Experience attached to target creature. The token has enchant creature and “Enchanted creature gets +2/+2.”
Whenever an enchanted creature you control dies, create a 3/3 green Elemental creature token.

Flash
When Agent of Deception enters the battlefield, counter target creature or planeswalker spell unless its controller pays {X}, where X is your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Flash
When Agent of Equilibrium enters the battlefield, destroy target creature or planeswalker an opponent controls that was dealt damage this turn.

Deception {1}{B} ({1}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
When Aguri, Shadow of Doubt enters the battlefield, target player reveals their hand. You choose a nonland card from it. That player discards that card. You lose 2 life.

Enchant land
When Aid from Martoob enters the battlefield, recruit. (Create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)
When enchanted land is tapped for mana, add one mana of any color.

Trample
When Ainok Scout enters the battlefield, nourish 2, then return a creature you control to its owner's hand. (To nourish 2, either put two +1/+1 counters on this creature or create two 1/1 white Citizen creature tokens.)

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
When Aith Aera Sentinel enters the battlefield, create a 1/1 green Elf creature token.

Vigilance
When Akrasan Sentry enters the battlefield, untap target creature.

When Alchemist's Kit enters the battlefield, you may return target creature to its owner's hand.
2U, Sacrifice Alchemist's Kit: Draw a card.

Deathtouch
When Aldrane's Masterpiece enters the battlefield, look at the top six cards of your library. You may put a Zombie card with lesser mana value from among them onto the battlefield. Put the rest on the bottom of your library in a random order.
Other Zombies you control get +1/+1.

When Alenian Cruel-Star enters the battlefield, put a +1/+1 counter on it if you control another Goblin.

When All-Blossom Memorial enters the battlefield, scry 1.
Prismatic — Whenever you cast a multicolored spell, you gain 1 life.
{T}: Add one mana of any color.

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

When Almgrove Librarian enters the battlefield, look at the top card of each of your libraries, then for each of those cards, put it on the top or bottom of one of your libraries.

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

(Choose only one work as a sorcery to add its ability.)
When Altar of Twisted Piety enters the battlefield, return target creature card with mana value 3 or less from your graveyard to the battlefield.
{2}{B}: Shadows Bind Us
{B}, Sacrifice three creatures: Create a 5/5 black Demon creature token. Put your choice of a flying counter or a lifelink counter on it. It can't block this turn.
{2}{R}: Hellfire Fills Us
{R}, Sacrifice a creature: Altar of Twisted Piety deals 2 damage to any target.

Flash
When Ambush Gharial enters the battlefield, it fights up to one target creature. If that creature would die this turn, exile it instead.

Reach
When Ambush Predator enters the battlefield, 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.

Flying
When Ameret's Favored enters the battlefield, you gain 3 life.

When Aminatou's Adherent enters the battlefield, 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.

When Amira, Grand Inventor enters the battlefield, create a 1/1 colorless Construct Artificer artifact creature token. If you control six or more artifacts, create a 6/6 colorless Golem artifact creature token instead.
Artifact tokens you control have all activated abilities of other artifact tokens you control.

When Ancestor's Skull enters the battlefield, target creature gets +1/+0 and gains menace until end of turn.
{2}, Sacrifice Ancestor's Skull: Target creature gets +2/+0 and gains menace until end of turn.