Isis, Nephthys and later on also Serket and Neith were essential in the regeneration sphere. They, as women/goddessees, played a crucial role in the process of resurrection in Ancient Egypt.
For that reason, ancient Egyptian artist included their images in every funerary artefact related with the mummy (at both ends of coffins and sarcophagi, in canopic shrines, ushabti boxes…).
Nevertheless, what happened under the reign of Akhenaton? During the Amarna Period the official religion changed into a kind of monotheism. The only officialy worshipped divinity was the sun disk Aten and every old divinity disappeared, included the goddesses.
How did they managed the matter of the resurrection and the women/goddesses involved in it?
The most important female figure in that period of the history of Ancient Egypt was Nefertiti. She had a higher status than former royal wives did, even in religion. Not only she had her own role in the cult to the Aten, iconography shows how it was considered that Nefertiti had a reviving power in herself.
The sarcophagus of Akhenaten is a clear proof of that. The image of Nefertiti appears at the four corners of the sarcophagus embracing the corpse from every point. Until that moment, Isis and Nephthys were depicted at both ends of sarcophagi and coffins.
However, once the Osirian theology disappeared and with it these two regenerating goddesses, it seems that Nefertiti took their role. For that reason her image appears in the king’s sarcophagus, because she could grant the resurrection of Akhenaten, as previously did Isis and Nephthys.
So, the concept remained, but it was reinterpreted under the Atenism.
This idea remains reinforced when we have a look at later sarcophagi of Tutankhamoun and Ay.
Once the traditional religion of Ancient Egypt was restored and ancient deities were again worshipped, the female responsible of the dead’s resurrection recovered their role.
That is why in the sarcophagi of Tutankhamun and Ay the four corners were occupied by Isis, Nephthys, Serket and Neith. The group of four goddesses who granted the dead’s resurrection were the subtitute of Nefertiti at the four corners embracing the mummy.