He's got some clues on how to destroy the artifact if you ask him about Marweth.
Return to Graystone yard and destroy the Sullonite artifact. Remember Ruhe's advice.
Approach the big pulsing statue on the docks and click it.
Marweth attacks.
This is a tough fight. Get her away from the relic. If you see her begin to spin, get out of the way, then continue to beat on her until she goes down to one knee.
When she's down healing, take a moment to smash the relic some more.