This article is from the Iron Maiden FAQ, by Vartan Narinian vsn@pobox.com and Steve Payne Sirpapa@aol.com with numerous contributions by others.
The origin of Osiris is obscure but by 2400BC Osiris played a double role:
He was both a god of fertility and the personification of the dead king.
This dual role was in turn combined with the Egyptian dogma of divine
kingship: The king at death became Osiris, god of the underworld; the dead
king's son, the living king, was identified with Horus, god of the sky.
Osiris and Horus, therefore, were father and son. The goddess Isis was the
mother of the king and was thus the mother of Horus and wife of Osiris.
The god Seth was considered the murderer of Osiris and the adversary of
Horus.
According to the most traditional form of the myth, Osiris was slain or
drowned by Seth, who tore the corpse into 14 pieces and flung them
over the earth. Eventually Isis and her sister Nephthys found and buried
all the pieces except the phallus, thereby giving new life to Osiris, who
thenceforth remained in the underworld as ruler and judge. Horus then
successfully fought against Seth and became the new king of Egypt.
Osiris was regarded as not only the ruler of the dead but also as the power
that granted all life from the underworld, from sprouting vegetables to
the annual flood of the Nile. From about 2000BC onward it was believed
that every man, not just the deceased kings, became identified with Osiris
at death. The process of becoming Osiris, however, did not imply resurrection,
for even Osiris did not rise from the dead. Instead it was the assumption
of immortality, both in the next world and through one's descendants on earth.
 
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