Nirvana

Whenever a nontoken creature enters the battlefield during your turn, you may search your library for a nonlegendary creature or
enchantment card with a lesser mana value and
exile it. For as long as it remains on the battlefield, the creature you control gains all the abilities of the exiled card. Then, put a +1/+1
counter on that creature and it becomes a
legendary Spirit in addition to its other types. Do
this only once on each of your turns.