You return to Tailfeather to inquire of Marcechamp what he knows about the deity of the Gnath.
This quest is available if you have completed the quest The Trine Towers.
Starting the Quest
Talk to Ysayle in the Dravanian Forelands to begin the quest.
Speak with Marcechamp
Before you go, be sure to attune to the Anyx Trine Aetheryte if you haven't already. Afterward, you can either teleport to Tailfeather or go east on foot to where the orange arrow is pointing in the minimap. Enter the building west of the bridge in Tailfeather and talk to Marcechamp. There will be a cutscene.
Obtain Hunks of Nanka Flesh
Go outside and walk north along the stream to exit the town. When you reach the part of the river that splits into two, go southwest along the other branch of the river to the orange circle on the map. The locations of Clearwater Nankas are marked in the minimap. Kill Clearwater Nankas until you have three hunks of Nanka Flesh.
Deliver the Hunks of Nanka Flesh
Go northwest to where the orange arrow is pointing in the minimap. Talk to Alphinaud to hand over the Nanka Flesh and complete the quest.
Next Main Scenario Quest
After you complete the quest, talk to Alphinaud to accept the next quest: The Nonmind. There will be a cutscene.