"Yorvo, He Big" enters the battlefield with four +1/+1 counters on it.
Whenever a green creature enters the battlefield under your control, put a +1/+1 counter on Yorvo. Then if that creature's power is greater than Yorvo's, put another +1/+1 counter on Yorvo.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
When Abbot of Keral Keep enters the battlefield, exile the top card of your library. Until end of turn, you may play that card.

Flying
When Abhorrent Overlord enters the battlefield, create a number of 1/1 black Harpy creature tokens with flying equal to your devotion to black. (Each in the mana costs of permanents you control counts toward your devotion to black.)
At the beginning of your upkeep, sacrifice a creature.

Trample
Abominable Treefolk's power and toughness are each equal to the number of snow permanents you control.
When Abominable Treefolk enters the battlefield, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Haunt (When this creature dies, exile it haunting target creature.)
When Absolver Thrull enters the battlefield or the creature it haunts dies, destroy target enchantment.

Flying
When Abyssal Horror enters the battlefield, target player discards two cards.

Kicker (You may pay an additional as you cast this spell.)
Flying
If Academy Drake was kicked, it enters the battlefield with two +1/+1 counters on it.

Academy Elite enters the battlefield with X +1/+1 counters on it, where X is the number of instant and sorcery cards in all graveyards.
, Remove a +1/+1 counter from Academy Elite: Draw a card, then discard a card.

This spell costs less to cast if you control a Wizard.
When Academy Journeymage enters the battlefield, return target creature an opponent controls to its owner's hand.

When Academy Researchers enters the battlefield, you may put an Aura card from your hand onto the battlefield attached to Academy Researchers.

When Acclaimed Contender enters the battlefield, if you control another Knight, look at the top five cards of your library. You may reveal a Knight, Aura, Equipment, or legendary artifact card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Fabricate 1 (When this creature enters the battlefield, put a +1/+1 counter on it or create a 1/1 colorless Servo artifact creature token.)

When Accursed Centaur enters the battlefield, sacrifice a creature.

Reach
When Acid Web Spider enters the battlefield, you may destroy target Equipment.

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
When Acidic Slime enters the battlefield, destroy target artifact, enchantment, or land.

When Acolyte of Affliction enters the battlefield, mill two cards, then you may return a permanent card from your graveyard to your hand.

Whenever you cast a spell with a squirrel in its art, you get {A} (an acorn counter).
Whenever a Squirrel you control enters the battlefield or dies, you get {A}.
, Pay X {A}: Target creature gets -X/-X until end of turn.
, Pay X {A}: Target creature gets +X/+X until end of turn.

When Acquisitions Expert enters the battlefield, target opponent reveals a number of cards from their hand equal to the number of creatures in your party. You choose one of those cards. That player discards that card. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

As Adaptive Automaton enters the battlefield, choose a creature type.
Adaptive Automaton is the chosen type in addition to its other types.
Other creatures you control of the chosen type get +1/+1.

Flash
Adaptive Shimmerer enters the battlefield with three +1/+1 counters on it.