Loa (also spelled lwa) are the spirits of Haitian Vodou and Louisiana Voodoo. They are also referred to as "mystères" and "the invisibles" and are intermediaries between Bondye (French: Bon Dieu, meaning "good God")—the Supreme Creator, who is distant from the world—and humanity. Unlike saints or angels, however, they are not simply prayed to, they are served. They are each distinct beings with their own personal likes and dislikes, distinct sacred rhythms, songs, dances, ritual symbols, and special modes of service. Contrary to popular belief, the loa are not deities in and of themselves; they are intermediaries for, and dependent on, a distant Bondye.
The word loa (or lwa) comes from the French "les lois;"the laws in English.
The enslaved Fon and Ewe in Haiti and Louisiana syncretized the loa with the Roman Catholic Saints—vodoun altars will frequently display images of Catholic saints. For example, Papa Legba is syncretized with St. Peter or St. Lazarus. Syncretism also works the other way in Haitian Vodou and many Catholic saints have become loa in their own right, most notably Philomena, St. Michael the Archangel, St. Jude, and John the Baptist.
In a ritual the loa are called down by the houngan (priest), mambo (priestess), or bokor (sorcerers) to take part in the service, receive offerings, and grant requests. The loa arrive in the peristyle (ritual space) by mounting (possessing) a horse (ritualist) in Creole referred as "Chwal" - who is said to be "ridden". This can be quite a violent occurrence as the participant can flail about or convulse before falling to the ground, but some loa, such as Ayizan, will mount their "horses" very quietly.