Following your return to Old Sharlayan, Y'shtola relays an invitation.
This quest is available if you have completed the quest Reunited at Last.
Starting the Quest
Talk to Y'shtola in Old Sharlayan to begin the quest. There will be a cutscene.
Speak with the Crystarium Gatekeep
Teleport to the Crystarium and use the Aetheryte to go to the Dossal Gate. Go up the stairs and talk to the Crystarium Gatekeep. Say Yes to proceed. There will be a cutscene.
Speak with Lyna
Talk to Lyna to proceed.
Speak with the Accomodating Official
Teleport to Radz-at-Han and use the Aetheryte to go to Meghaduta. Go to the quest icon and talk to the Accomodating Official. There will be a cutscene.
Speak with Y'shtola
Talk to Y'shtola to proceed.
Head for Meghaduta
Go west and use the Aethernet Shard to go to Meghaduta, then go northeast to the quest icon. Talk to Varshahn to complete the quest. There will be a cutscene.