Must be at least level 65 and able to speak Draconic Language.
Speak with Arbiter Selek on the island between Cacotoxic Stain and the Drednever Crash Site. It's a small island in between the cloud travel. You will have to time your jump but if done correctly you will land on the small island with the Arbiter on it. The only was off will be either suicide, evac, or call out. The Arbiter will send you to get a tome from "The Vaults of El'Arad"
Examine the book on a desk at the north end of the room Korgo the Vault Keeper is in. ( 170, 57, -33 ) When you have theb ook, you need to kill Korgo. Return to Arbiter Selek to complete the quest once this is done.
This opens up the next quest in the series "High Crimes"