The quest starts when you reach a room in which Lord Arhu is imprisoned. Speak with him and you learn that he is here because of Linder Kemm. He also wants you to leave him be.
Your task is to free Arhu. Use Spirit Vision. You can see three ghosts that hold Arhu. Absorbing energy of each one of them will destroy the bonds.
Save Lord Arhu and defend yourself from Black Ring. Linder Kemm himself will also join the fight. Keep Arhu alive at all cost. The best way to do that is to teleport him to a place that is far away from the battlefield.
Even if Arhu dies you can still get information from him about The Cathedral but you won't get any additional piece of equipment.
Reward: 96,950 experience points + 3 guaranteed rewards + 1 out of 3 to choose from depending on your character's class (optional)