You deliver the arcane epistle to Baderon, who agrees to decipher it for you.
This quest is only available if you started the game in Limsa Lominsa, and you have completed the quest Men of the Blue Tattoos.
Starting the Quest
To start the quest, talk to Baderon in the Drowning Wench in Limsa Lominsa. It's north of the Aftcastle aetheryte. There will be a cutscene.
Deliver the Note to Reyner
The next destination is in the Marauders' Guild, which is north of where you are now. Give Reyner the note from Baderon.
Travel to Swiftperch and Speak with Ryssfloh
The next destination is in Swiftperch. If you didn't attune to the aetheryte there, you can get there by using the aetheryte outside of the Marauders' Guild to go to the Zephyr Gate, or if you didn't attune to all the aetherytes in Limsa Lominsa, you can use the Marauders' Guild aetheryte to go to the Limsa Lominsa Aetheryte Plaza, and go east from there to reach Middle La Noscea. From there, you will need to make the long journey northwest to Western La Noscea, and from there, southwest to Swiftperch.
In Swiftperch, talk to Ryssfloh to start the instanced battle.
Solo Duty: Feint and Strike
The battle will begin after a cutscene. First, attack the Drowned Outrangers (ranged enemies are weaker than melee enemies). Then attack the Drowned Brawlers, but soon there will be more enemies that arrive through the town gate. Attack the Drowned Diviner to stop her from healing her allies. Then kill the Drowned Outrangers at the town gate, and once they are gone, attack the Drowned Brawlers. However, a Blanga will eventually appear. Keep it away from your allies, and focus your attacks on it. If there are any Drowned Brawlers after you kill the Blanga, kill them to end the fight.
After this, there will be a cutscene, and then you will be face-to-face with a Lesser Gargoyle. After you have brought its HP down, Y'shtola will come to help. When the Lesser Gargoyle dies, the Masked Man will attack. Y'shtola will help heal and protect as you fight.
There will be another cutscene. This one is important, so you might want to pay attention. You can go to an inn room and use The Unending Journey to watch it again if you wish.
Report to Reyner
Go back to the Marauders' Guild in Limsa Lominsa and talk to Reyner. There will be a cutscene. Be sure to watch this one (or at least rewatch it in the inn later if you skip it). Afterward, you receive a Lominsan Ring, which is exclusive to players who started in Limsa Lominsa.
Next Main Scenario Quest
After completing the quest, talk to Reyner to accept the next quest: High Society.