Is Gudul Lurker legal in Standard, Modern, and Commander?

Gudul Lurker is legal in: Modern, Pioneer, Legacy, Vintage, Commander.

What type of card is Gudul Lurker?

Gudul Lurker is a Creature — Salamander. Its oracle text reads: "This creature can't be blocked. Megamorph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)"