Today's Know Your Lore subject hasn't yet been seen in World of Warcraft, but he's the Big Bad in the upcoming Cataclysm expansion, making his first appearance in the series since Warcraft II. An ancient and incredibly powerful being with a past swathed in betrayal and destruction, Deathwing is poised to bring about the second-largest cataclysm that Azeroth has ever seen.
Who: Neltharion the Earth-Warder, aka Deathwing the Destroyer.
What: Colossal, nearly-molten black dragon. Officially a Dragon Aspect, one of five sent to guard ancient Kalimdor by the Titans. He's also the head of the Black Dragonflight.