Is Baron Sengir legal in Standard, Modern, and Commander?

Baron Sengir is legal in: Legacy, Vintage, Commander.

Baron Sengir

Q: What type of card is Baron Sengir?

Baron Sengir is a Legendary Creature — Vampire Noble. Its oracle text reads: "FlyingWhenever a creature dealt damage by Baron Sengir this turn dies, put a +2/+2 counter on Baron Sengir.{T}: Regenerate another target Vampire."

Legendary Creature — Vampire Noble

Flying<br>Whenever a creature dealt damage by Baron Sengir this turn dies, put a +2/+2 counter on Baron Sengir.<br>: Regenerate another target Vampire.