Go to the spire and click the portal to enter. Kill all mobs until Quozz spawns. Kill the named and return to the spires to speak to Firiona Vie.
Note[]
The exit from the zone may become invisible sometime during the action. If you use /loc clipboard to record your zone-in point then return to this point after destroying the interstice and wave your "hand" around you should be able to find it.
Zone-in in my instance was at ( -32, 0, -3 ) Copy/waypoint -32, 0, -3.3.
Alternatively, camping to character select then logging back in will effectively exit you from the zone.
If all else fails, "call home" and then return to Obol Plains to complete the quest.
