Easy: Damien makes himself sick with laughter as he watches the Divine and the Dragon Knight throw insults at each other. Whilst he is distracted an unlikley hero sneaks up behind him & deals the death blow; your creature! DK and Divine stop fighting, look at each other and shrug. Game over.
Seriously though having played DKS I'm not bothered either way who kills Damien. I know Lairan are making two games and Ill be buying the dragon knight '3D Divinity 2 style' one as I feel more of a connection with that game and my character. Especially if it will allow you to import your DKS character playable or not. It's a long, long time since I played Divinity 1 so much so I've pretty much forgotten it. Top down view games i.e. the other 'Divinity'3' game do not really interest me anymore. But that's just me.