The Murder of Osiris
Set, jealous of his brother Osiris (the rightful king), lured him to a banquet. Set brought a coffin that he had measured to Osiris's exact size; when Osiris lay down in it, Set seized him, wrapped him in the coffin, sealed it with lead, and threw it into the Nile. The chest washed down-river and out to sea, washing up in Byblos, where a tamarisk tree grew around it [S3]S3 · Plutarch, On Isis and Osirisc. 79 CEtextOpen source ↗[S4]S4 · Hornung, 'The Ancient Egyptian Books of the Dead' / 'Nile Religion' (academic)modern (translation & scholarship)academic.
Ancient Egyptian religion spanned three millennia. There is no single 'official' version: Heliopolitan, Memphite, and Hermopolitan creation traditions coexisted and are presented in parallel, not merged into a genealogy that never existed.
The 'Byblos' episode is a later addition to the myth [S3]S3 · Plutarch, On Isis and Osirisc. 79 CEtextOpen source ↗[S4]S4 · Hornung, 'The Ancient Egyptian Books of the Dead' / 'Nile Religion' (academic)modern (translation & scholarship)academic.