While the last of things are dealt with here, you will journey to Castrum Oriens.
This quest is available if you have completed the quest Bereft of Hearth and Home.
Starting the Quest
Talk to Conrad in Rhalgr's Reach to begin the quest.
Speak with Raubahn
Use the nearby Aethernet Shard to go to the Northeastern Rhalgr's Reach Aethernet Shard, then go to the quest icon on the map to talk to Raubahn.
Speak with Lyse
You can either teleport to Castrum Oriens, or you can use the nearby Aethernet Shard to go to the Fringes Gate, then go west to where the orange arrow is pointing in the minimap. Talk to Lyse and 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 Alphinaud
Talk to Alphinaud to complete the quest.
Aether Current Quest
With the completion of this quest, you can now start the blue quest "The Hidden Truth" in the Fringes. Completing that quest will attune you to an Aether Current in this area.
Next Main Scenario Quest
After you complete the quest, talk to Alisaie to accept the next quest: Lies, Damn Lies, and Pirates. There will be a cutscene.