The Undergoddess for the Niger River is Oya according to Yoruba mythology. She may also be called Yansan, and the full name is Oya Yansan which has the meaning "mother of nine." According to legend, all the cemeteries are hers. Some believe the cemeteries are her home, while others believe that she is the gatekeeper who allows the dead to enter. She is powerful, and is the ruler of the dead. Her elements are whirlwinds and tornadoes, especially those that come with lightning. As a warrior she battles at the side of Shango who is the god of thunder, lightning and fire. Her feast day is on February 2, and her symbols include the horsetail fly-whisk and a number of masks.

Olodumare is God in the Yoruba religious system. Olodumare may also be called Eledumare, Olorun, Olofin-Orun and Eleda. The manifestation that the God assumes is called an Orisha (Orisa or Orixa) which is just a spirit or deity. Historically, African slaves could not freely practice their religion, so they “disguised” their gods with the slave owner gods, mostly the Catholic saints. The West African Yoruba people recognized three spiritual forces: a supreme creator god (Olodumare), messenger spirits similar to angels (the orishas) and the spirits of the dead.

Syncretism means combining different beliefs. Santeria evolved as a syncretic religion with origins in the Caribbean. Slaves were prohibited from practicing their religion, so they synchronized their African gods with the names of the Catholic saints. The one All Mighty God is called Olodumare, and he created the other entities that correspond to the Catholic saints. The religion is a combination of Catholicism and West African Yoruba beliefs, and it may also be called La Regla Lucumi, Regla de Ocha or Lukumi. The belief system does not have a central creed like most religious practices. Instead, the religion is understood in terms of the rituals and ceremonies that are commonplace.

The ruler of the dead in Yoruba mythology was at one time barren or could only bear premature children. She makes a sacrifice from the rainbow colored Sacred Cloth. From that she births nine children, and then she is called Iyansan, the "Mother of Nine." The number nine becomes her sacred number which is related to the creative process. Premature children and barrenness are symbolic of a woman's journey through the creative process. The multicolored cloth represents the variety of aspects a woman must consider before birthing a creative idea. In other words, the "cloth of many colors" represents the gestation process that is needed for ideas to mature.

The Atlantic slave trade transported West African natives into Cuba, Puerto Rico and other Caribbean locations. The slaves brought their religious beliefs which were banned by the slave owners. To keep the true roots of their beliefs hidden, this syncretic religion evolved using ideas from the Roman Catholic religion.