Cid proposes relocating to Mor Dhona to prepare for your rescue attempt, since it is closer to Castrum Centri.
This quest is available if you have completed the quest Notorious Biggs.
Starting the Quest
Talk to Cid in Monument Tower in the southwest part of Coerthas Central Highlands to begin the quest.
Speak with Slafborn
Exit the tower. If you go slightly north, then go southeast, you will reach the path that leads directly to Mor Dhona from Coerthas Central Highlands.
Once in Mor Dhona, go southwest and attune to the Aetheryte if you haven't already. Then talk to Slafborn, who is near the Aetheryte. There will be a cutscene.
Speak with Glaumunt
You will find Glaumunt nearby to the east. Talk to him to complete the quest.
Next Main Scenario Quest
After you complete the quest, talk to Glaumunt to accept the next quest: Getting Even with Garlemald.