Acidic Slime

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

Carven Caryatid

Defender (This creature can't attack.)
When Carven Caryatid enters, draw a card.

Conclave Naturalists

When Conclave Naturalists enters, you may destroy target artifact or enchantment.

Volo, Guide to Monsters

Whenever you cast a creature spell that doesn't share a creature type with a creature you control or a creature card in your graveyard, copy that spell. (A copy of a creature spell becomes a token.)