Is Vitality Hunter legal in Standard, Modern, and Commander?

Vitality Hunter is legal in: Legacy, Vintage, Commander.

Vitality Hunter

Q: What type of card is Vitality Hunter?

Vitality Hunter is a Creature — Nightmare. Its oracle text reads: "Lifelink {X}{W}{W}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.) When this creature becomes monstrous, put a lifelink counter on each of up to X target creatures."