##Curses come with a heavy cost##
Curses come with a heavy cost
Curses are powerful magic, and powerful magic comes with a cost. All but the simplest curses also need some kind of intelligence to guide them; either some kind of supernatural being overlooking them, like a god or a demon, or the curse has a spirit bound into it.
If a curse is cast as a spell or ritual, there may be extensive human sacrifice involved, or the caster must sacrifice some of their power or life force to create the guiding spirit.
A witch of the cursing kind has typically made a deal with a demon or dark god to gain power, usually for a limited time (e.g. until death, but each use of magic ages the witch) or with a limited store of power. The witch pays the price, and the demon or god effectuates the curse.
Then there is the dying curse; usually considered the most powerful sort. In this case, the curser (knowingly or unconsciously( dedicates their soul to a higher power in return for the curse, or they become a spirit that oversees the curse - similarly to how extreme hate or anguish at death will turn the dead person's soul into a ghost that haunts a place until given release.
The cost associated with curses limits their use. It is not something done lightly. Also, spirits may only be bound into a curse for a limited time before they dissipate, die or can break free, and demons or dark gods may eventually tire of the game. The stronger the curse, the longer the term may be.
