Atusa's Legs is a quest items in Divinity: Original Sin 2.
Location: Atusa's corpse
When you use Corpse Eater on it: Learn Fortify, and get some lore about about Atusa.
During dialog with Kniles the Flenser: Pacifies him. Fane can acquire the Face Ripper.
You can feed it to Buddy; it will make him upset.
- As of the most recent patch, eating the leg no longer grants a skill.
Should you hold onto the leg while either within the fort or even after escaping it, you can find yourself in the sewers; also called "Kniles's Playground." Within' you will meet a Magister character by the name of "Kniles the Flenser" who will begin a dialog and quite creepily sniff out the leg still in your bag, and demand that you hand it over to him. If Fane is in your party, he’ll ask for Kniles’ face ripper in exchange.