He seems to have somewhat unique AI in that he has phases, like a boss. At about 60-70% health, he will use his shield's skill, then two-hand his tooth. After this, he will never, ever one hand it, although he will, amusingly, try to block with the tooth, generally getting guard broken after only a couple of hits. His lightning absorption will also drop dramatically when he uses his shield's skill (great time to use miracles or other lightning projectiles), but it will return to normal when the skill ends. Also, if you interrupt his use of the skill, he will immediately try again, and again, and again, until he succeeds, which can be exploited.