Curse

Some of the most popular and effective weapons among fey, hags, and linnorms are curses. Breaking a curse is generally a difficult, potentially puzzling challenge. Suffering a curse can be the result of a minor spat of bad luck or part of learning a hard lesson about respecting the power of nature. Some particularly unforgiving fey, such as some daoine sidhe or wild hunters, will curse mortals on sight in sylvan settings. They may even curse mortals without their knowledge in order to manipulate them from behind the scenes. Spirits of bloodshed and conflict, such as the baen nighe, use this tactic to influence the outcome of battles.

Examples:

1. A mortal accidentally breaks a nymph’s taboo by unknowingly entering her sacred grove. As punishment, she curses him to never enjoy the blessings of the earth for a year and a day. Unless he gets a remove curse spell cast by a higher-level spellcaster, the victim cannot eat any food grown from soil. It withers away to dust in his mouth.

2. Heroes vanquish a mighty Unseelie countess or dread linnorm, only to discover that the death of this wicked being has left her killers 
cursed to be painfully vulnerable to future enemies with similar tactics until the curse is dispelled by an even more powerful spellcaster.