I believe that an illusion mask might help...a troll in our guild was KoS first time he went into Katta (for the Shissar Organs quest, not the rallic pack one, but maybe it's the same idea). With a halfling mask he was no longer KoS, but the turn-in still failed. I would suggest TRYING the mask, seeing if you can get in and talk to the NPC without being attacked. If you can get to him without being attacked, hail him and go through the dialogue to be sure you can do the quest, BEFORE doing any turn-ins.