This page explains how to complete the level 90 post-Endwalker quest "The Dark Throne".
This quest is available if you have completed the quest Abyssal Dark.
Starting the Quest
Talk to Y'shtola on Mare Lamentorum to begin the quest. There will be a cutscene.
Speak with Urianger
Teleport to Bestways Burrow or go north to where the orange arrow is pointing in the minimap. Talk to Urianger to proceed.
Speak with the Accommodating Official
Teleport to Radz-at-Han and use the Aetheryte or an Aethernet Shard to go to Meghaduta. Go northeast to the quest icon and talk to the Accommodating Official. Say Yes to proceed. There will be a cutscene.
Speak with Varshahn
Talk to Varshahn to complete the quest. There will be a cutscene.
Next Main Scenario Quest
After you complete the quest, talk to Varshahn to accept the next quest: Seeking the Light. There will be a cutscene.