Speak to Earthcaller Torunscar at the Ring of the Elements.
I can't believe it, <name>. Me own son - me own flesh and blood! Throwing his lot in with those fiends from the Twilight's Hammer. Did you see what he became when he tried to destroy the wedding? Oh ... why? Why?
It's that beast, <name>. The enormous mouth emerging from the earth to our west. "The Maw of Madness!" My son said it spoke to him, but I thought it was just nightmares.
The Earthen Ring is trying to destroy it. Go to Earthcaller Torunscar, west of here, and see how you can help!