A creature that ends its turn adjacent to the boiúna must succeed a DC 23 Charisma saving throw or have its shadow stolen from it. Starting on its next turn, and every hour thereafter, a creature that has its shadow stolen must succeed a DC 23 Constitution saving throw or gain 1 level of exhaustion. If the boiúna is killed or if remove curse is cast on a creature whose shadow has been stolen, its shadow returns and they no longer need to save against gaining levels of exhaustion, but any exhaustion already accrued remains. The boiúna can suppress or regain use of this ability as a bonus action.