Is Brokkos, Apex of Forever legal in Standard, Modern, and Commander?

Brokkos, Apex of Forever is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

Brokkos, Apex of Forever

Q: What type of card is Brokkos, Apex of Forever?

Brokkos, Apex of Forever is a Legendary Creature — Nightmare Beast Elemental. Its oracle text reads: "Mutate {2}{U/B}{G}{G} (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.) Trample You may cast this card from your graveyard using its mutate ability."

Legendary Creature — Nightmare Beast Elemental

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.)