Kongo religion (Kikongo: BuKongo) encompasses the traditional beliefs of the Kongo people. Due to the highly centralized position of the Kingdom of Kongo, its leaders were able to influence much of the religious practices across the entire region. As a result, many other ethnic groups and kingdoms in West-Central Africa, like the Chokwe and Mbundu, adopted Bakongo spirituality. The spirituality is based on a complex animistic system and a pantheon of spirits. The principle Creator God of the world is Nzambi Mpungu, the sovereign master, and his female counterpart, Nzambici. While Nzambi Mpungu, who gave birth to the universe and the spirits who inhabit it, is vital to the spirituality, ancestor veneration is the core principle. The Bakongo cosmos is split between two worlds: the top half representing the physical world, or ku nseke and the bottom half representing the spiritual world, or ku mpèmba. Expert healers, known as Banganga, undergo extensive training to commune with the ancestors in the spiritual realms and seek guidance from them. Bantu mythology The religion of the Kongo is deeply complex. According to historians John K. Thornton and Linda M. Heywood, "Central Africans have probably never agreed among themselves as to what their cosmology is in detail, a product of what I called the process of continuous revelation and precarious priesthood..." The Kongo people had diverse views, with traditional religious thought best developed in the northern Kikongo-speaking area. There is plenty of description about Kongo religious ideas in the Christian missionary and colonial era records, but as Thornton states, "these are written with a hostile bias and their reliability is problematic". Generally, these traditions are oral rather than scriptural and passed down from one generation to another through folk tales, songs, and festivals, include belief in an amount of higher and lower gods, sometimes including a supreme creator or force, belief in spirits, veneration of the dead, use of magic and traditional African medicine.