Is Avatar of Woe legal in Standard, Modern, and Commander?

Avatar of Woe is legal in: Modern, Legacy, Vintage, Commander.

What type of card is Avatar of Woe?

Avatar of Woe is a Creature — Avatar. Its oracle text reads: "If there are ten or more creature cards total in all graveyards, this spell costs {6} less to cast. Fear (This creature can't be blocked except by artifact creatures and/or black creatures.) {T}: Destroy target creature. It can't be regenerated. Power/Toughness: 6/5"