On Hell difficulty, each of the act bosses hasa chance to drop an Essence. Andariel and Duriel drop Twisted Essences of Suffering. Mephisto drops Charged Essences of Hatred. Diablo drops Burning Essences of Terror. Baal drops Festering Essences of Destruction. Transmute one of each to create a Token of Absolution, which will allow you to reset your attributes and skills.