With the completion of the Ultima Weapon, Gaius has offered an ultimatum to the Eorzean Alliance: surrender or die.
This quest is available if you have completed the quest Escape from Castrum Centri.
Starting the Quest
Talk to Minfilia at the Ul'dah Airship Landing to begin the quest. (If you are outside of the airship landing, you can speak with Elyenora in the airship landing area to reach Minfilia.)
Speak with Bartholomew
Talk to the Arrivals Attendant to exit the arrivals area. Go north and talk to Nanahomi, and go to the Hustings Strip. Go east, and turn right at the archway. Go around the circle until you can go southwest to the quest icon. Talk to Bartholomew. There will be a cutscene. This one is important, so it is recommended to watch it either now or via the Unending Journey in an inn room.
Speak with Minfilia
Use a Vesper Bay Aetheryte Ticket (which you received after completing the quest Back from the Wood) to return to Vesper Bay.
Go into the northwest building, then go down the stairs to enter the Waking Sands. Go east and into the Solar. Talk to Minfilia to complete the quest. There will be a cutscene.
Vesper Bay Aetheryte Tickets
Upon completion of the quest, you will receive 8 more Vesper Bay Aetheryte Tickets.
Next Main Scenario Quest
After you complete the quest, you will need to be at least level 49 to proceed to the next quest. After you reach level 49, talk to Minfilia to accept the next quest: Operation Archon. There will be a cutscene.