Is Necropanther legal in Standard, Modern, and Commander?

Necropanther is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

Necropanther

Q: What type of card is Necropanther?

Necropanther is a Creature — Cat Nightmare. Its oracle text reads: "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."

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.)