From the front page of the PDF:
A Masked Lord needs adventurers to journey to the Gates of the Moon and retrieve a protective artifact. This quest is surely for the good of Waterdeep, but what will it mean for those who lose their ancient guardian? A Living Forgotten Realms adventure set in Waterdeep and the Astral Sea for characters of the Paragon tier (levels 11-20).
This adventure is the beginning of the Brightcloaks Major Quest and assumes that the events of the Restoring Splendor Major Quest have already occurred. The Brightcloaks series continues with WATE3-2 and concludes with WATE3-3. Players are encouraged to use the same PC and to play the three parts of this trilogy in order.