Curses

The vast majority of powers run by the soul that created the effect suppling the power. A curse is a different beast: A parasite on the soul. They require great skill to originate, but not much strength (which is why **** curses are popular): A clever bit of magic connects to the soul of a victim, and draws on the host soul's strength to both maintain the curse itself and to produce the desired effect(s) of the curse. Consequently, a curse can never be stronger than the host soul (if it needs more power than the host provides, it quickly collapses). Thus a curse on a civilian is going to be sharply limited in power, while a curse on a powerful hero(ine) may be very potent indeed.

Hostile curses are generally eventually contrary to the caster's goals, however, for a subtle reason: It exercises the victim. Sooner or later, a cursed individual will develop their own powers, often, but not always, in a form related to the curse.

Despite the classification, not all curses are hostile: "Curse" is a classification of method (although most curses are hostile). While seldom used for such, they can be a way for a skilled user to grant minor power to a friend or underling.