Is Fires of Undeath legal in Standard, Modern, and Commander?

Fires of Undeath is legal in: Modern, Legacy, Vintage, Commander, Pauper.

What type of card is Fires of Undeath?

Fires of Undeath is an Instant. Its oracle text reads: "Fires of Undeath deals 2 damage to any target. Flashback {5}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.) *"I drink of those who are worthy of my palate. The rest I burn."*"