According to an Egyptian myth, the wise god Osiris was promised to become the king of gods by Ra, his father. But this made his brother Set jealous. Set lured Osiris into a trap, murdered him and cut his body into pieces. Then Set spread the body parts to all the corners of Egypt.
Isis, Osiris’ wife was terribly sad when she heard this and she started on a journey. She found all the body parts and put them back together in order to mummify his complete body. Thanks to this, Osiris became god of the afterlife.
The Egyptians believed that when they died, they had to ask Osiris for the entrance to the paradise where the gods lived. But getting to paradise was not easy. The dead had to travel through the underworld, face terrible monsters and repeat difficult spells. To prepare themselves for this journey the Egyptians wrote all the rules down in the Book of the Dead.