Kat's dad was an Alchemist. He was trying to find a way to make himself immortal. The tests he did on himself failed, but one thing he did right was made his little, what's called a Kitsune ball. It holds spirits and can be absorbed for immortality.

Basically, in story, they found it amongst his old junk in Toni's basement, and here's Kat holding it. YAY

Kat and Concept are totally mine :3