The Madness of the Jewel King allows Ace to change the lifespan of his subordinates into jewels of a similar value. In particular, he provides his men with a special collar with a jewel in it, which cannot be equipped without their own discretion. Upon wearing it on the neck, the collar cannot ever be taken off again. When Ace activates his ability on his target, the jewel on the person's collar illuminates as they eventually dies. Afterwards, jewels of a proportionate "value" to the victim's lifespan will materialize on his palm.