Myth of the Nile River
The original form of the myth states that Osiris was killed by a wooden sarcophagus secretly being made to his measurements by Set, who was jealous of Osiris's positon as king, and so plotted to kill him and take his place. A party had been held where the coffin was offered to whomever could fit inside. A few people tried to fit in, but to no avail. Osiris was encouraged to try, but as soon as he lay back, the lid slammed on him and was locked. It was then sealed with lead and thrown into the Nile.
Upon hearing that Osiris was gone, Isis set out to look for him. She later learned that the coffin had floated down the Nile river up to the coast of Byblos (now in modern day Lebanon) and got embedded in the trunk of a cedar tree. She also learned that the cedar tree had been taken and used as a pillar to support a palace for the king of Byblos.
After explaining the situation to the queen of Byblos and getting her permission, she managed to extract the coffin without harming the palace and took Osiris' body out into the desert and buried him back in Egypt.
Again, Set found Osiris' coffin, took his body out, and dismembered him into 13 parts, scattering them across the land of Egypt. Each part represented one of the 13 full moons seen each year (there are roughly 13 lunar months per year).
Once again Isis set out to look for the pieces and she was able to find and put together 12 of the 13 parts, but was unable to find the 13th, which was eaten by the oxyrhunchus fish (a fish with an unusual curved snout resembling depictions of Set). Instead, she fashioned a phallus out of gold and sang a song around Osiris until he came back to life.
Osiris was resurrected. So it was that Isis conceived Horus. Due to this experience, Osiris became Lord of the Dead, and the Afterlife.
