Is Polukranos, Unchained legal in Standard, Modern, and Commander?

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

Polukranos, Unchained

Q: What type of card is Polukranos, Unchained?

Polukranos, Unchained is a Legendary Creature — Zombie Hydra. Its oracle text reads: "Polukranos enters with six +1/+1 counters on it. It escapes with twelve +1/+1 counters on it instead. If damage would be dealt to Polukranos while it has a +1/+1 counter on it, prevent that damage and remove that many +1/+1 counters from it. {1}{B}{G}: Polukranos fights another target creature. Escape—{4}{B}{G}, Exile six other cards from your graveyard."