Necropanther
Creature — Cat Nightmare
Mutate 
(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.)
Whenever this creature mutates, return target creature card with converted mana cost 3 or less from your graveyard to the battlefield.
3/3
Illustrated by
Ikoria: Lair of Behemoths#196UncommonEnglishLegality
Rulings
Apr 17, 2020
If a card in a player’s graveyard has 
in its mana cost, X is considered to be 0.