Necropanther

Mutate {2}{W/B}{W/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.)
Whenever this creature mutates, return target creature card with mana value 3 or less from your graveyard to the battlefield.

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Ikoria: Lair of Behemoths

If a card in a player’s graveyard has {X} in its mana cost, X is considered to be 0.