Hoop of the Standing Promise

This plain iron hoop is polished smooth on the inner face, broken only by a hairline gap where its ends nearly meet. Spoken promises seem to linger around it; after an oath is sworn, the metal gives a faint tightening pressure against the ear until the words are fulfilled or betrayed.

The DR is greedy and will not share with any other magic. Each charge is spent on the wearer's turn by speaking one promise aloud with a witness present. Until that promise is kept or broken, to a limit of 24 hours, the wearer cannot be knocked unconscious and is not reduced below 1 hit point. Breaking the promise ends it at once and costs 2d6 damage. The hoop closes over its gap when depleted, and the wearer always knows whether a promise made to them has been broken.