Phantom Wasteland

Phantom Wasteland is the primary world area for a Seeker's Rest story on N'Erud. Defeating the area's mini boss grants access to your second Seeker's Key.

Ascension Spire

At Seeker's Rest, the floating, octopod robot directed you to find him in his tower, the one with "a glowing white orb held aloft to the heavens." It was talking about the Ascension Spire, and this is what you're looking for:

Just outside the tower entrance is the Ascension Spire World Stone (Remnant II)#World Stone. Inside is a large room where you'll find a humanoid standing in front of a relief depicting several, strange creatures. This is the Custodian:

If you speak with him, he introduces himself and gives you your task, ".

Seeker's Key

Completing the Seeker's Rest story quest requires three Seeker's Keys. You found the first when you entered N'Erud at Seeker's Rest.

The second is somewhere in the Phantom Wasteland. Its exact location is random, but it is always in a Seated Colossus just like the one you found at Seeker's Rest:

This is always just past the exit from the Phantom Wasteland mini boss fight.