Curses take a Psyche slot and must be removed through rituals.

Curse of the Night Hag. A bitter evil is overtaking your soul. Make a save every time you sleep. On a failure, write the name of one of your companions in your psyche. If your psyche is full, forget something that is not the curse. You gain advantage on your actions against the named companion(s) until the curse is lifted.

Originated by a Hag