"Long before the creation of Sanctuary, the Eternal Conflict between angels and demons raged on for untold millennia. Blizzard Entertainment teamed up with renowned director Peter Chung and acclaimed animation studio Titmouse to create this unique vision of a fundamental moment in the battle between the High Heavens and the Burning Hells."
A bit of other interesting Diablo 3 tid-bitery comes from a recent Joystiq article about just how many...

Great video thanks for sharing.
Yeah, I thought it was awesome too! Apparently Angels can be goaded.
Video was great. It was done by the same guys who do Metalocalypse. It would have been a step up though if they added a heavy metal soundtrack.
Haha yeah, especially when Imperius cleaves Diablo in half.
Honestly, I'm not really interested in Diablo III, so I'm not sure why I clicked on this video...
But CRAP!, that was cool.
Diablo 3 launch day: I have to work until 8pm and be back at work at 6:30am. Great timing.
Apparently even with one day shipping amazon says D3 will arrive the 17th... I may never pre-order from Amazon again.
Live learn I guess.