This Troper does the same thing with his characters to an extent. One is a girl who can conjure and manipulate fire. Downside, she's constantly burning her skin off whenever she uses it. Upside, it regenerates immediately after she stops using it, and comes back baby-soft and twice as sensitive. In the same story, the protagonist is the unwilling host of an
Eldritch Abomination that takes the shape of a black trench coat. A possible inversion is that whenever he's sexually aroused (or exposed to violence), this abomination takes over his mind and body, granting him the ability to manifest an infinite amount of blades, mouths, and tentacles of various sizes(from microscopic to large enough to slice open a planet).