Is Nethroi, Apex of Death legal in Standard, Modern, and Commander?

Nethroi, Apex of Death is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

Nethroi, Apex of Death

Q: What type of card is Nethroi, Apex of Death?

Nethroi, Apex of Death is a Legendary Creature — Cat Nightmare Beast. Its oracle text reads: "Mutate {4}{G/W}{B}{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.) Deathtouch, lifelink Whenever this creature mutates, return any number of target creature cards with total power 10 or less from your graveyard to the battlefield."

Legendary Creature — Cat Nightmare Beast

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.)