There is a scene of the Book of the Dead from the tomb of Ay, in which are depicted on the solar boat the gods of the Heliopolitan cosmogony and the Myth of Osiris (apart from Seth): Re-Horakhty, Atoum, Shu, Tefnut, Geb, Nut, Osiris, Isis, Horus…and out of the boat Nephtys stands alone apart from her fellows. Why?
Isis and Nephtys were usually represented together. They were a perfect divine team in Ancient Egypt for the favour of the Osiris’ resurrection. They were always depicted both collaborating together for the corpse’s resurrection.
However, Nephthys had in some way a secondary role and maybe not the same prestige as her sister Isis.
Firstly, Isis was the wife of Osiris, the dead god, so she supported the main responsability in the regeneration of her husband’s body. Isis, although assisted by Nephthys, was the one who made the ancient Egyptian mourning ritual on the mummy of Osiris for restoring his vital faculties.