osiris4dOverview. Osiris, the Mhty One, was both god of the dead and a central fure of Egyptian mythology.His cult arose around 2600BCE, as those of competing deities,Osiris, lord of death, with crown atef and green body. In Egyptian mythology, Osiris is the god of life, death, the flooding of the Nile, and the afterlife.He was the brother and husband of