Is Thrashing Mudspawn legal in Standard, Modern, and Commander?

Thrashing Mudspawn is legal in: Legacy, Vintage, Commander.

What type of card is Thrashing Mudspawn?

Thrashing Mudspawn is a Creature — Beast. Its oracle text reads: "Whenever this creature is dealt damage, you lose that much life. Morph {1}{B}{B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)"