A loa (pl. loa) is a type of spirit native to the incorporeal realm, highly focused on ritual (particularly that of the voudou religion). They are intermediaries for the god Bondye. An individual loa's strengths and weaknesses can vary, depending on which family they are from:
Loa are incorporeal. They can assume a human shape for brief periods of time, but the strain of this forces them to return to a possessed body (or to the spirit world) afterwards to rest. Most often, when encountered in the corporeal realm, loa are possessing a human or animal host. They speak with their own voices in these forms.
As spirits, loa can be harmed by iron (with the exception of the Nago family, which can be defeated in combat, but is not harmed by iron). An unbroken line or circle of salt will act as a barrier to a loa, and cannot be crossed - certain mixes of goofer dust may also be effective barriers.
Loa cannot be killed in the material world, however they can be exorcised or banished with the proper rituals (though they usually willingly leave their hosts to return to the spirit world). If they are in the material world without a host body, they can be dispersed. They can also be destroyed, but what whatever is used to destroy them must be able to bridge the corporeal and incorporeal realms. Aside from this possibility, loa are immortal and unchanging.
Like all spirits, loa exist most solidly in the spirit world. However, they can be summoned into the material world, as long as they have a host, or do not stay for long. Loa cannot cross into the material world without invitation. Everything to do with loa is highly ritualized - they must be summoned a certain way, and must be served or given assistance before they will aid the summoner.
Most loa display a particular behavior or say certain phrases while possessing a host, and can thus be recognized. A loa possession is referred to as "mounting the horse", with the possessee being described as "ridden". The host body's soul is not displaced in this process. Generally, mounting the horse is willing for both parties - however loa are powerful spirits, and can overpower most human souls if it comes down to it. Mounting the horse can be a quiet and subtle process, or very violent, depending on the individual loa involved - sometimes the host will spasm, convulse, and collapse.
All loa have the ability to call on Bondye, the leader of their family, and other loa.
Even when a spirit's true form is not visible to the naked eye, it will appear in a mirror. If they are possessing someone, this image will appear as an overlay of the body's reflection.
Society and Habitat
Loa are grouped into families or nations (known as nanchons). Each family has a leader, known as an Iwa, and they rule the family. Loa of that family follow their edicts.
Ghede loa are associated with death and fertility, and the colors black and purple. They follow the Barons (La Croix, Samedi, Cimitière, Kriminel) and Maman Brigitte. In general they are loud, rude (though not outright insulting), highly sexual, and fun. Having already lived and died, they are quite fearless, and to show off this confidence they will often perform feats while mounted - eating glass, for example, or spreading chili rum over their sensitive areas.
Kongo loa are associated with the colors black and blood red, and are believed to originate from the Congo. They follow the greatly feared Marinette, though the family also includes the many Simbi loa (serpent loa). There is some connection between the Kongo and Petro Loa, as Marinette began as a Loa of the Petro family before being made Iwa.
Nago loa are associated with the colors green and black, and are believed to originate from Nigeria. They follow Ogoun, and through him are martial spirits associated with iron, hunting, politics and war.
Petro loa are associated with the color red, and are believed to originate from Haiti and the New World, possibly due to the harsh treatment of slaves in the area. They follow Ezili Dantor, as well as Met Kalfu, the Master of the Crossroads. They are fiery and warlike, often aggressive.
Rada loa are associated with the color white, and are associated with the gods of Africa. They are older and more beneficent than the other loa families. They include Legba, Loko, Ayizan, Anaisa Pye, Dhamballah Wedo and Ayida-Weddo, Erzulie Freda, La Sirène, and Agwe.