In Astria Ascending, speak with Egyl at Harmony Orchard after making Kaydin an Assassin to obtain The Wings of the Snake side quest.
Defeat Attor in Windam
Fast travel to Windam and speak with Attor who is to the left of the Weapon Shop. After a brief scene, a fight will trigger. Defeat him in battle.
Go back to talk to Egyl in the Harmony Orchard
Return to Egyl and speak with him.
Find Egyl’s informer in the Air Country
From the Aquarius Temple Entrance fast travel point in Archipelago, follow the top of the path (along the greenery) west then north. A large open area will be on your left as you’re heading north. When the greenery curves to the west, head slightly west then go directly south once you see the edge of the path below you. Keep heading south until you see a red glowing orb on the west side just before the path curves west.
Interact with it to trigger a cutscene. A fight will follow. Defeat the enemies.
Talk to Duka in Windam
Head to the Weapon Shop in Windam and speak with Duka.
Pay 600 Lums to Duka in Windam
Speak with him again when you have 600 Lums.
Go back to talk to Egyl in the Harmony Orchard
Return to Egyl at Harmony Orchard and speak with him.
Defeat Teshi at the Gemini Temple
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Rewards: Hydor x1, Life Core x3, Omni Elixir x1 and 5,000 Lums