Mindleecher

Mutate {4}{B} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.) Flying Whenever this creature mutates, exile the top card of each opponent's library face down. You may look at and play those cards

for as long as they remain exiled.

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6o72rh48lvpb1hihm21crf.