I tried to kill that shaman all the time, but because of certain abilities he had, he was extremely difficult to corner and kill (or catch off guard) and was also a very careful character. His abilities counteracted much of my abilities at the time. I never grouped with him, but used him to assist me in killing other priests and when I could, I attacked him. He commented me on a number occasions that he was hunting or wanted peace, but I still attacked him. Unfortunately, I wasn't a huge damage outputter nor could I lag him effectively and I usually hunted by myself, so I failed.

In short. An enemy of my enemy (who is my enemy) is my friend (until I can find a moment where he is weak and kill him myself). Hope that answers my question.