All the mystery Schools are different in their beliefs, their rituals and their doctrines and we know very little about them. However there is also an evident line of continuity that is apparent in many ways. In Ancient Egypt, the most important and influential god and goddess, but far from the only ones, were Osiris and Isis. Osiris, an Egyptian King or Pharaoh, was killed by his brother, Set, who took his place on the throne. However Set was defeated in his turn by Isis and Horus, respectively Osiris’ wife (and sister) and son. Horus becomes the next Pharaoh, ensuring the continuity of the dynasty. Isis, with the help of some other gods, such as the Sun God (Re-Atum), and her sister Nephthys, recovered Osiris’ body, saved it from decomposition, and had it mummified. It was a kind of resurrection or rebirth for Osiris, but he did not come back on earth and, instead, became the ruler of the next world. He was also the God of Fertility who ensured the fertility of the land along the Nile River. Isis is described as the mother goddess who guarantees an orderly succession to the throne of Egypt. She is also remembered for her womanly virtues. Each time a pharaoh died, his subjects enacted a mortuary rite based on the myth of Osiris’ death. It was believed that what happened to Osiris could be symbolically re-enacted during the ceremony of their embalmment for the eternal survival of each dead pharaoh.
Initially these ceremonies were reserved exclusively to the dead pharaohs, but the important rulers of the kingdom were soon allowed to have them too. Later on, the cult was allowed to everybody who could bear the cost. In this way a great number of dead people were given the proper funerary rituals of mummification and burial that would allow them to hope for spiritual resurrection after being united, mystically, with Osiris. The Mysteries of Osiris and Isis were introduced in Greece and, also, in the Roman Empire. There they took the usual form attributed to the Mystery Schools of the past: they were secret organisations that only accepted initiated people among their members.