Speak to Magister Sang about what happened; afterwards you can kill him for 1,700 Experience. (He is dying anyways and he asks you to kill him so don't feel bad!)
If you don't have any source points on you, there is a source fountain in the corner of the room; get some and cast Bless on the level as it is cursed. The doors will now swing open for you and the quest will begin.
Interact with the shrine while having a source point on your main character. (900 Experience)
Pick up the Corrupted Tyrant's Helm from inside the shrine; this will advance the quest Artifacts of the Tyrant and finish the quest The Armoury.