Oh look, it's another Dungeon Siege III trailer, and it's brought co-op!
This video shows off the four player characters, working together to stop Looten Plunger, Dr. Blight, Verminous Skumm and Sly Sludge. Or I may have gotten this game confused with Captain Planet. It happens sometimes.
In any case, there's a bunch of monsters and fighting to gawp at, so go do it.