The cult of Isis originated in Egypt and went through two major stages. In its older Egyptian version, which was not a mystery religion, Isis was regarded as the goddess of heaven, earth, the sea, and the unseen world below. In this earlier stage, Isis had a husband named Osiris. The cult of Isis became a mystery religion only after Ptolemy the First introduced major changes, sometime after 300 B.C. In the later stage, a new god named Serapis became Isis’s consort. Ptolemy introduced these changes in order to synthesize Egyptian and Greek concerns in his kingdom, thus hastening the Hellenization of Egypt.

From Egypt, the cult of Isis gradually made its way to Rome. While Rome was at first repelled by the cult, the religion finally entered the city during the reign of Caligula (A.D. 37-41). Its influence spread gradually during the next two centuries, and in some locales it became a major rival of Christianity. The cult’s success in the Roman Empire seems to have resulted from its impressive ritual and the hope of immortality offered to its followers