Shoot him, and then the night terrors that pop up. You have to shoot him again to get the next night terror to spawn --- I follow people around on their slow mounts and say "CAN'T LET YOU DO THAT, STAR FOX!" -Cereburus Q
Wabbajack everything is right. But here are the details: 3 trials (don't remember the name of each but) 1 - Summon fight: Forget about the fight and shoot Pelagius on the other side of the arena. 2 - Sleeping Pelagius: Shoot him, and shoot whatever attacker appears so it transform into something harmless. Repeat until complete. 3 - Confidence vs Fear: Shoot confidence to make it bigger and bigger, shoot fear to make it smaller and smaller. Shoot extra attackers.