I'm afraid I can't go into the specifics of how or why they work, as I don't have the ability to use them. But from what I can tell, curses are usually a matter of gathering the right ingredients and giving them your energy, and dark magic physically drains your opponent.

I'm assuming that jumble next to your words is supposed to be a face of worry. Dark magic and curses may sound bad, but they can be used for good purposes.