The Hom-Dai was used by the ancient Egyptians only to punish the worst blasphemers that committed severe crimes, and so was used very rarely, if at all. Although the curse was mentioned in any form of text, there was no written case of it ever actually having been performed. This is because the Egyptians greatly feared it, and the sole known cause of the Hom-Dai ever being carried out was on that of the High Priest Imhotep.
He committed the crime of using the Book of the Dead to bring back his lover, the Pharaoh Seti I's mistress, Anck-Su-Namun, from the dead. The Hom-Dai was meant to be so potent a curse that should any of its victims ever arise, with them would come forth the Ten Plagues of Egypt, as God himself had set unto Egypt in biblical times. The victim would also be condemned to a cursed life that would not end, even in death. And although a person cursed with the Hom-Dai might be physically dead, they were still capable of being brought back to life through an incantation from the Book of the Dead.
Bound to the victim's existence was a chest that, should it ever be opened, would leave those that opened it bound to the curse of the Hom-Dai. As the original victim would seek out whoever was present when the chest was opened, so as to kill them and assimilate their organs and fluids. By doing this, the original Hom-Dai's victim would regenerate themselves to their original state of being, and no longer be undead, but a being with unspeakable powers and immortality. Until the victim is fully regenerated, they will fear the presence of cats, who are the guardians of the underworld in Egyptian mythology.
But in order for to prepare the Hom-Dai, it began by first cutting the person's tongue out. They were then mummified alive with scarabs, which would eat them very slowly and painfully. Reading an incantation from the Book of the Dead resurrects the cursed individual, giving them the power of invincibility, but condemning them to be a spreader of pestilence. A passage from the Book of Amun-Ra removes the immortality from the cursed individual, leaving them vulnerable and subject to being killed.
