Warhammer: Chaosbane

Still a working glitch.
1.Launch on normal difficulty
2.Your friend starts Chaos 5
3.You die first, but don't give up and wait
4. A friend dies immediately after you, gives up and leaves
5. Click Surrender, then No and start the battle again, but alone.
The difficulty of the battle will be Normal, but the game will perceive it as Chaos 5

Video for clarity.

I did it for Bragi, without the glitch, on the first boss. Dressed him in a set of tests and two Tory fire rings for kickbacks to turn on immortality, every 5-7 seconds =). Killed him very quickly.