The lwa are organised into nanchon, nations, named for the African regions and peoples from which they came — Rada from Dahomey by way of the Yoruba-Fon world, Nago from the Yoruba, Kongo, Ibo, and Petwo, which was created in the Caribbean. The two major divisions are Rada and Petwo, and the contrast is temperature rather than morality: Rada lwa are cool, old, deliberate, dependable and slow; Petwo lwa are hot, fast, dangerous, expensive and effective. Petwo is generally understood by scholars and by practitioners to have been forged under slavery — its lwa are angrier and its rhythms harder, and it includes spirits with no African antecedent. Crucially the same person serves both, often in the same ceremony with a break between, and there are problems that only a Petwo lwa will take on. Reading the division as good versus evil is the commonest outside error.