Bring the Fathom Core to Je'neu Sancrea at Zoram'gar Outpost, Ashenvale.
The Twilight's Hammer has moved into the Moonshrine Ruins of Blackfathom Deeps. Their presence can only serve to coerce the elements into working against us. If left unchecked, this region will be theirs for good.
[player], go into Blackfathom and find the ruin's fathom stone; it should be somewhere close in the water. In it is a fathom core - a device that when properly read it will relate a history of all elemental activity. If I have it, I and the Earthen Ring can maybe do something to stop them!