Is Cadaverous Knight legal in Standard, Modern, and Commander?

Cadaverous Knight is legal in: Legacy, Vintage, Commander, Pauper.

Cadaverous Knight

Q: What type of card is Cadaverous Knight?

Cadaverous Knight is a Creature — Zombie Knight. Its oracle text reads: "Flanking (Whenever a creature without flanking blocks this creature, the blocking creature gets -1/-1 until end of turn.){1}{B}{B}: Regenerate Cadaverous Knight."

Creature — Zombie Knight

Flanking (Whenever a creature without flanking blocks this creature, the blocking creature gets -1/-1 until end of turn.)<br>: Regenerate Cadaverous Knight.