After the events at the Tower of Zot, you consult with Thancred about how to proceed.
This quest is available if you have completed the quest Tipping the Scale.
Starting the Quest
Talk to Thancred in Thavnair to begin the quest. There will be a cutscene.
Speak with Varshahn
Go northeast to where the orange arrow is pointing in the minimap. (When you reach the cliff, go north until you can go northeast.) Speak with Varshahn to proceed. There will be a cutscene.
Speak with Thancred
Talk to Thancred to proceed.
Speak with Thancred in the Main Hall
Teleport to Old Sharlayan and use the Aetheryte to go to the Baldesion Annex. Go into the building and check on the Main Hall Entrance. Say Yes to enter the Main Hall. Talk to Thancred to complete the quest.
Next Main Scenario Quest
After you complete the quest, you will need to be at least level 81 to proceed to the next quest. After you reach level 81, talk to Krile to accept the next quest: In the Dark of the Tower. There will be a cutscene.