How to get this quest
This quest is available in Trademond's Adventurers' guild after completing Festival Of Greed.
Reaching the avian
After the scene with the hermit, you can take two path to reach the empowered avian:
Note that there will be wind slowing your progression whatever you choose. The direction of the wind can also affect combat.
Fighting the avian
If you pilfer all of the empowered avian's gold before the fight, the avian will fight with the ENRAGED debuff and won't fly. But the wind makes this pretty hard without any flash bomb use.
If you fight the empowered avian without stealing the gold and don't want to remove Aura's collar, a advised strategy is to exploit Desmond's passives. Apply an anti-magic on Desmond to mitigate Storm III and make him use blessed bombs to give him a good damage output. Aura should use Thunderbolt to complement this damage output. Guard when the enemy is preparing a powerful attack, and the fight should be won relatively quickly.
Quest reward
After defeating the avian, you automatically go report to the hermit. If you have Theft II, you get the following choices:
If you don't have Theft II, no choice appears and you take the second option by default. Note that you can enter the hermit's cabin later to steal the catalyst once you have Theft II.