The final battle rolled around; I killed the four demons whilst Jon ripped apart three of my party members. Then nadia shot him with a kua-toa bolt and he froze, stunned! (i had lowered his resistence earlier). My lead hero hacked him to bits, and then....nothing....nada...zip. The room was strewn with corpses and my surviving three party members just stood there and scratched their heads. whats going on? I cant leave hell either...

Grumlin

When u kill Jon he says something before he falls down and while stunned, he can't talk. His dialogue triggers some endgame movies and if he doesn't say nothing, nothing happens!

So, you're out of luck pal, kill him again and this time without stunning him!

I know its easier said than done but you can do it!