During the Old Kingdom period, the pantheons of individual Egyptian cities varied by region. During the 5th dynasty, Isis entered the pantheon of the city of Heliopolis. She was represented as a daughter of Nut and Geb, and sister to Osiris, Nephthys, and Set. The two sisters, Isis and Nephthys, often were depicted on coffins, with wings outstretched, as protectors against evil. As a funerary deity, she was associated with Osiris, lord of the underworld, and was considered his wife.
A later myth, when the cult of Osiris gained more authority, tells the story of Anubis, the god of the underworld. The tale describes how Nephthys was denied a child by Set and disguised herself as her twin, Isis, to seduce him. The plot succeeded resulting in the birth of Anubis. In fear of Set's retribution, Nephthys persuaded Isis to adopt Anubis, so that Set would not find out and kill the child.
The tale describes both why Anubis is seen as an underworld deity (he becomes the adopted son of Osiris), and why he could not inherit Osiris's position (as he was not actually the son of Osiris but his brother Set), neatly preserving Osiris's position as lord of the underworld. It should be remembered, however, that this new myth was only a later creation of the Osirian cult who wanted to depict Set in an evil position, as the enemy of Osiris.
Set flung the box in the Nile so that it would drift far away. Isis went looking for the box so that Osiris could have a proper burial. She found the box in a tree in Byblos, a city along the Phoenician coast, and brought it back to Egypt, hiding it in a swamp. But Set went hunting that night and found the box. Enraged, Set chopped Osiris's body into fourteen pieces and scattered them all over Egypt to ensure that Isis could never find Osiris again for a proper burial. Isis and her sister Nephthys went looking for these pieces, but could only find thirteen of the fourteen. Fish had swallowed the last piece, his phallus.
She created a golden phallus, with the help of Thoth, and attached it to Osiris’s body. She then transformed into a kite and with the aid of Thoth’s magic conceived Horus the Younger. The number of pieces is described on temple walls variously as fourteen and sixteen, and occasionally forty-two, one for each nome or district
Mother of Horus