Something like:
- Defeat Slurgal without letting anyone die
- Defeat Xada after letting him transform
Blink and you missed it: kill a boss in under 20 seconds
I can't find any boss with low health enough to down within 20 seconds, unless if you also mean mini-bosses, however, I'm sure that coding this for mini-bosses would be a nightmare if not outright impossible.
Dance macabre
*Danse
Main Boss Ch 6 in under 20 seconds:
http://www.youtube.com/watch?v=raksg9J4pN0&feature=player_detailpage#t=905s
From first hit to death is about 18 seconds, from start of event till death is I think just bordering on 20 seconds.
Thanks for the Danse correction... when I first came across the phrase it was as "dance macabre" and I clearly didn't notice the play on words