Just throwing this out here: Diplomacy works only against NPCs. While I think that noone would disagree that an Ice Assasin is an NPC for this purpose, I think it could be argued that the Shism (I think that's what it was) of Jeremy is a PC, as it would be fully controlled by the player (I think), so it would not turn hostile. Not sure if it changes anything1, but it popped into my head this morning and I wanted to post this.
1 I've stopped understanding the actual builds several pages ago, just looking on for the pure carnage.Originally Posted by D20 SRD, emphasis mine