The Witcher 2: Assassins of Kings[]
Harpy feathers are used to craft the following items:
Swords[]
Armor[]
Associated quest[]
The Witcher 3: Wild Hunt[]
Harpy feathers is an alchemy ingredient. It is not needed to craft anything but can be dismantled into monster feather.
It is a random drop from harpies, and guaranteed from their monster nests and erynias who guard them. In the Blood and Wine expansion, it can also be found as regular random loot in the Witch of Lynx Crag's hut during A Knight's Tales.