Enter the Tower of Frozen Shadow ( -1116, -526, -1719 ) /waypoint -1116, -526, -1719 and attempt to find any information relating to Tserrina's intentions. This can be done with a cleared instance even if the player with the cleared instance already did this step.
Find a piece of Tserrina's notes, at ( 16, 217, -20 ) /waypoint 15.85, 217.47, -20.26 in Shadowed Corridors on the Third Floor: The Shadowed Barracks.
Find a second set of Tserrina's notes, at ( 77, 290, -13 ) /waypoint 76.92, 290.28, -13.46 in Darkness Rising in Umbral Halls. Accessible by falling down the hole and running up the spiral ramp.
Find the last part of Tserrina's notes, at ( 14, 561, 38 ) /waypoint 13.64, 560.97, 37.54 in VhalSera's Dominion in Umbral Halls.
Search for a tome relating to the Age's End prophecy, at ( -94, 75, -72 ) /waypoint -94, 75, -72 in Shadowed Corridors on the Second Floor: The Frozen Library.