How were Nephilim mummified after the Pact with Menes?

In the backstory for the Pact with Menes, it was explained that the agreement stipulated that the Nephilim would be allowed to incarnate within royal bloodlines after which they would be mummified along with their Simulacrum and entombed within prepared tombs that would allow them to retain consciousness after death and continue progression towards Agartha.

How did this actually work? As the Simulacrum is dying, the Pentacle enters "Semket" (a misreading of msktt) and then exits the body. For mummification to work as described, the Pentacle would need to be prevented from exiting the body first before any mummification could begin! 

I'm skimming through the third edition French Minor Arcana book, which said the Promethean Mysteries within the priesthood embalmed the Simulacrum to trap the Nephilim inside, but it doesn't seem to explain this either.

So I'm going to provide an explanation for my campaigns.

The Pact with Menes required the assistance of amenable Selenim necromancers, who would later form the Unnamed Arcanum. They created amulets worn by the royal bloodlines, which would interrupt and prolong Semket to kept the Pentacle inside the body when it died and was mummified. The mummification process itself was devised by the necromancers of the mortuary cult as a means to preserve the Solar-Ka against decay, allowing the body's soul (or some semblance thereof) to persist indefinitely. There were other secret societies involved as well, who sought to keep the Immortals imprisoned this way. 

These amulets could perhaps preserve Selenim against death, allowing at least some Selenim to be mummified and entombed... of course it's also possible that they were placed in suspended animation within their tombs rather than outright mummified. See Serpent Moon for an example.

The Pharaonic Immortals also practiced temporary incarnation within idols and animals, reminiscent of shamanism and sarcophagi (cf. here and here), in which they embodied deities to influence the population. This is where the Egyptian belief in objects inhabited by Ka comes from, and why iconoclasts routinely broke off parts of statues: this interfered with the use of magic relying on the symbolism of intact objects, particularly scrying magic and inhabitation.

When Egypt's mummies and other artefacts were later plundered by grave robbers and European colonial powers, countless mummies were destroyed so that they could be ground up and eaten as ineffective "medicines" or unwrapped and desecrated at dinner parties for the perverse entertainment of decadent Victorians. Of course, this resulted in the release of many mummified or otherwise trapped Immortals who had yet to reach Agartha, their Elemental Pentacles (and Black Moon Cores?) preserved by stasis items also buried with their mummies.

Hope you enjoyed!