Arbiter

This item is a small metal rod with a small red button on the top of it. When pressed, the button causes a red ball of light to appear over the wielder's head. Arbiters are used in one style of duel. When the red ball of light extinguishes the wielder is considered "out."

The ball of light extinguishes under the same rules as losing concentration on a spell, with the caveat that a creature can concentrate on both a spell and an arbiter.