Get out and run. After clearing the Scoured Reach, swap to a flying mount and return to Diamant.
Completing this quest bumps players up to Friendly with the Therazane faction. Therazane herself comes by to check in!
Therazane says: Is this the one you're wasting your time with, Diamant?
Diamant the Patient says: Not wasted, Stonemother. It has been very useful. It's alreay killed many Twilight.
Diamant the Patient says: It stands to reason that it may be here for exactly the reasons it says it is.
Therazane says: Then you take responsibility for its actions, Stone Lord. You will be the one answering to me when it shows its true intent.
Therazane says: And you, fleshling, consider for a moment that you are entirely surrounded by rock in this place. The very earth you walk on bends to my will.
Therazane says: If you betray us, there will be no escape for you. I will crush your body so slowly that you shall hear every single one of your bones break.
Therazane says: I'm glad we had this talk.
Diamant the Patient says: You still have much to prove. But it seems you've brought the stone. That is an excellent start.
Diamant the Patient says: The other Stone Lords have already heard my words. They should show you a degree of trust. At least enough so that you can prove yourself.
Additionally, the siege upon the Temple of Earth has ceased. Huzzah!