Wait...were you able to get things to work? He probably has a ton of hitpoints and it always takes a lot of hits for demi-liches. Please confirm so that if I need to make some changes, I can log this to be fixed.
He should have one more change after that...
I was not be able to kill Lord Garrax/Demi-Lich in "regular way" for now, but I used a cheat for kill him!!! I used CTRL+Q (he join my party), then I used Shadow Keeper and I modified his HP (I set at 9) and then kick off Lord Garrax/Demi-Lich from my party. There was a cutscene and then he changed his form in a Dragon, then I beat the Dragon (CTRL+Y)!!!!!
OK at least everything went well as far as finishing the quest so I will look into the Garrax guy some more.
What were his hitpoints when you forced him into the party...before setting them to 9?
EDIT: I ask because I do not believe that you got him down to low enough hitpoints in combat.
Edited by Hoppy, 17 October 2010 - 09:48 AM.