OK for this quest, there is nothing inside the Troll Chamber (Archeological Site). It's just to finish up the quest for Gula. By restoring Gula back to his original self, he will give you a quest item which you can interact for the 3rd clue.
I can't really remember if it was him giving you the item, or he gives you the key to his chest in his room. Either way, you will have the 3rd clue item.
