Lake of Kalandra: Crafting League?
Kalandra wants all sorts of powerful treasures. She's willing to help you make items you bring to her powerful, but with a price: She wants the original. After you use her power to craft a powerful item, she will take the original, and give you a mirrored copy.
That's why we're getting an Oil that lets us change the Anointment of a mirrored item.
The perfect downside for a perfect crafting mechanic.