How bad is it? It's one of Uwe Boll's better films. Adequate, if long and unoriginal.
Should you see it? Probably not.
Supposedly based on the video game Dungeon Siege, this is just a rip-off of Lord of the Rings (and there are even two sequels). There's adequate production design - the film budget was reportedly $60,000,000 - and a capable cast: Jason Statham, Leelee Sobieski, Colin Ford, John Rhys-Davies, Ray Liotta, Burt Reynolds, Ron Perlman and Will Sanderson. What it lacks is originality and interest. An evil sorcerer wants to rule, so he has half man/half beast creatures attack. A farmer (named "Farmer") has his son killed and his wife abducted, so he gathers together comrades and fights back. Uwe Boll manages some adequate battle scenes, but you've seen better. Did I mention there are ninjas? The question remains: how does this director keep making expensive films that don't make money?