Osiris (Egyptian Wsir) is the god at the centre of the Egyptian understanding of death. The myth holds that he once ruled Egypt as a good king, was murdered and dismembered by his jealous brother Seth, was restored by his wife Isis, and passed not back to the throne of the living but to the rule of the Duat, the realm of the dead. He does not return to life as he was; he becomes the king of a different country, the guarantor that the dead, too, can live.
This gave every Egyptian a share in a god's fate. Through the proper rites the deceased was identified with Osiris, called the Osiris [name] in funerary texts, and hoped, like him, to be vindicated and to live on. The story explained, in mythic terms, the promise the whole funerary apparatus was built to secure: that death, correctly met, need not be the end.
His conflict with Seth also gave Egyptian kingship its charter. The living pharaoh was Horus, the son who avenges the father and inherits the throne; the dead pharaoh became Osiris. Each royal succession re-enacted the myth, and the legitimacy of the reigning king rested on being Horus to his predecessor's Osiris.