Divine Journey

Brand it. But calculate in advance so that the item can be retrieved (and doesn't just end up stuck in the center of the cell).

The creature catches fire, continues to thrash its arms even more violently, and after a while, it stops completely, falls to the bottom of the cell, and continues to burn. The item falls out of the chamber – it's just a pendant with a picture of an elderly human woman on it. On the other side, it says "with love, to my beloved son."