This page explains how to complete the Endwalker Main Scenario Quest "In the Dark of the Tower".
This quest is available if you have completed the quest The Satrap of Radz-at-Han, and have reached level 81.
Starting the Quest
Talk to Krile in Old Sharlayan (in the Main Hall of the Baldesion Annex) to begin the quest.
Speak with Nahbdeen
You can either teleport to The Great Work in Thavnair and go north to the quest icon on the map. or you can go outside and go northeast to the nearest building, and go inside and talk to Kytte to teleport to Thavnair (you won't get aether sickness anymore) then go northwest to where the orange arrow is pointing in the minimap. Talk to Nahbdeen to proceed.
Stand by at the Boat
Go northwest to the quest icon on the map and check on the sparkling Destination to proceed. There will be a cutscene.
The Tower of Zot
Use the Duty Finder or Duty Support to enter The Tower of Zot. Please see the The Tower of Zot Guide for a walkthrough.
After you complete the duty in The Tower of Zot and exit the area, there will be a cutscene.
Speak with Thancred
Talk to Thancred to complete the quest.
Next Main Scenario Quest
After you complete the quest, talk to Thancred to accept the next quest: The Jewel of Thavnair.