At this year's BlizzCon, Blizzard released a flashy new cinematic trailer for Diablo III. In the trailer, Deckard Cain's niece Leah uncovers a dark new threat to the world of Sanctuary. Hint: it's another demon.

Leah has a vision of an enormous demon called Azmodan. He's searching for something called the Black Soulstone. His minions will soon invade the mortal realm in search of the stone. It's not clear what this item does, but it'd probably be a good idea not to let Azmodan get it.

Azmodan is the Lord of Sin. He's one of the four Lesser Evils that overthrew Diablo, Mephisto and Baal (the Prime Evils) and banished them to Sanctuary. The three Prime Evils were then slain in the events of Diablo and Diablo II. I'd assume Diablo makes a return in the third installment - I mean the game carries his name after all. Perhaps the Black Soulstone revives him and his brothers?

Diablo III is expected in early 2012. You can get the game for free by signing up for a year of World of Warcraft.