Acid Web Spider

Reach
When this creature enters, you may destroy target Equipment.

Fleetfoot Panther

Flash
When this creature enters, return a green or white creature you control to its owner's hand.

Blasting Station

{T}, Sacrifice a creature: This artifact deals 1 damage to any target.
Whenever a creature enters, you may untap this artifact.

Ambush Krotiq

Trample
When this creature enters, return another creature you control to its owner's hand.

Teferi's Veil

Whenever a creature you control attacks, it phases out at end of combat. (While it's phased out, it's treated as though it doesn't exist. It phases in before you untap during your next untap step.)

Aether Channeler

When this creature enters, choose one —
• Create a 1/1 white Bird creature token with flying.
• Return another target nonland permanent to its owner's hand.
• Draw a card.

Ainok Guide

When this creature enters, choose one —
• Put a +1/+1 counter on this creature.
• Search your library for a basic land card, reveal it, then shuffle and put that card on top.

Prison Term

Enchant creature
Enchanted creature can't attack or block, and its activated abilities can't be activated.
Whenever a creature an opponent controls enters, you may attach this Aura to that creature.

Hixus, Prison Warden

Flash (You may cast this spell any time you could cast an instant.)
Whenever a creature deals combat damage to you, if Hixus entered this turn, exile that creature until Hixus leaves the battlefield. (That creature returns under its owner's control.)

Ajani's Welcome

Whenever a creature you control enters, you gain 1 life.

Deceiver Exarch

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, choose one —
• Untap target permanent you control.
• Tap target permanent an opponent controls.

Aethersnipe

When this creature enters, return target nonland permanent to its owner's hand.
Evoke {1}{U}{U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Cavern Harpy

Flying
When this creature enters, return a blue or black creature you control to its owner's hand.
Pay 1 life: Return this creature to its owner's hand.

Bloom Hulk

When this creature enters, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Mirror of Life Trapping

Whenever a creature enters, if it was cast, exile it, then return all other permanent cards exiled with this artifact to the battlefield under their owners' control.

Acquisitions Expert

When this creature enters, 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.)

Teferi's Honor Guard

Flanking (Whenever a creature without flanking blocks this creature, the blocking creature gets -1/-1 until end of turn.)
{U}{U}: This creature phases out. (While it's phased out, it's treated as though it doesn't exist. It phases in before you untap during your next untap step.)

Doomsday Specter

Flying
When this creature enters, return a blue or black creature you control to its owner's hand.
Whenever this creature deals combat damage to a player, look at that player's hand and choose a card from it. The player discards that card.

Agent of Treachery

When this creature enters, gain control of target permanent.
At the beginning of your end step, if you control three or more permanents you don't own, draw three cards.

Aggressive Biomancy

Create X tokens that are copies of target creature you control, except they have "When this token enters, it fights up to one target creature you don't control."

Aether Adept

When this creature enters, return target creature to its owner's hand.

Alchemax Slayer-Bots

When this creature enters, tap target creature an opponent controls and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)