After the banquet in Ul'dah, Raubahn has an important task for you to fulfill.
This quest is only available if you started the game in Ul'dah, you have completed the quest A Royal Reception, and have reached level 15.
Starting the Quest
Talk to Raubahn in the Hall of the Flames, south of the Ul'dah Aetheryte Plaza, to start the quest. There will be a cutscene.
Speak with Momodi
Go back to the Adventurers' Guild and talk to Momodi. There will be a cutscene.
Speak with Elyenora
If you have attuned to all of the aetherytes in Ul'dah, you can use one to go directly to the Airship Landing. If not, it is recommended to do so, but until then, go west from the Adventurers' Guild, then go south until you find Willahelm, the Lift Attendant. Talk to him and ride the lift to the Airship Landing.
At the Airship Landing, talk to Elyenora. Say Yes to proceed to the landing area.
Board the Airship
Check on the gangplank, then say Yes to board the airship.
Speak with the Storm Honor Guard
Go down the path on the right and talk to the Arrivals Attendant. Say Yes to leave the landing area. Go forward and talk to the Storm Honor Guard.
Present Raubahn's Missive in Limsa Lominsa
Speak to Blanmhas, the Lift Attendant, and choose to go to Bulwark Hall. Turn left and follow the path out to the main aetheryte of Limsa Lominsa. Attune to it. It is recommended to attune to all the aetheryte crystals in Limsa Lominsa when you have the chance to do so.
Go back the way you came, to the quest location marked on the map and minimap. Talk to Zanthael and hand over the Letter to the Admiral, and there will be a cutscene.
Speak with L'nophlo
Your next destination is the Airship Landing in Limsa Lominsa. The door to the lift is on the other side of this room. Go there and talk to Grehfarr, and ride the lift to the Airship Landing. Once there, talk to L'nophlo and say Yes to proceed to the landing area.
Board the Airship in Limsa Lominsa
Follow the path to the gangplank. Check on it and say Yes to board the airship.
Speak with the Serpent Honor Guard
Follow the wooden bridge into the building and talk to the Arrivals Attendant. Say Yes to leave the landing area. Go forward and talk to the Serpent Honor Guard.
Present Raubahn's Missive
Turn around and go up the stairs. Go out the door on the left, then turn left and follow the path. Go north up the hill and you will see the main aetheryte of Gridania. Attune to it. It is recommended to attune to all the aetheryte crystals in Gridania when you have the chance to do so.
Go through one of the north gates to proceed to Old Gridania. The quest destination is there, near the Conjurers' Guild aetheryte. Talk to the Silent Conjurer and hand over the Letter to the Elder, and there will be a cutscene.
Next Main Scenario Quest
After completing the quest, talk to the Serpent Officer to accept the next quest: Call of the Sea.