I did theorise about it for a while. That Thief of Heart might hijack shiny powers, as powers seem to be a soul function. Maybe they need to actually get a soul of a person to be able to use some of their abilities... But I always figured that there would be a ridiculous ammount of side-effects like with timetravel. Wouldn't that make ToH a great devil kind of character? The one who coaxes you into selling your soul so that they get a delicious power rush?

Huh, that could definitely be a thing! Again, I am not sure how factible Stealing Powers would be, but I do like the idea of a Devil-like character. I mean, a Devil-like character, aside from Doc Scratch.