“Usually given to mortals in exchange for their service, geases grant power, with a kick-in-the-teeth exception that comes upon you when you least expect it. Like, you're invulnerable, except to an arrow made of the heartwood of a hawthorn tree, which just so happens to be the exact kind of arrow that your worst enemy favours. Or you'll win every battle you're in, but you're not allowed to refuse invitations to dinner, so if someone invites you to dinner right before a battle, you're not going to be able to show up for that fight.”