What Lies Within

You have been deceived by Orthalak the Depraved! Destruction of the Amulet has unleashed a terrible Daemon that threatens the Dark Elves' chance to claim control of the Vortex. You must hunt down this Daemon before any of his plans can come to fruition. Before vanishing, Krothaak mentioned that the Shadow would be his first target. Thinking on this, it seems clear that the Daemon was referring to the Ritual of Ulgu, the Wind of Shadow, to the north.

Travel to the Shadowfall Ruin, northeast of the Ritual of Shadow. Defeat the Horrors and Flamers who serve Krothaak, and when the Daemon appears, defeat him as well. When done, return to Orthalak the Depraved in Saruthil's Wake to inform him his plan has failed.