The Tem-akh is a spiritual shard of the souls of the old mummies, like the Shemsu-Heru, that were destroyed once the Dja-akh smote the Dark Kingdom of Sand. Each tem-akh incorporates the strongest aspect of the ancient soul it once bound to.
After that, the tem-akh dispersed across the world, searching for mortals with a hole in their soul (called Hamartia) that would make them unbalanced before Ma'at. The tem-akh can bind with the incomplete soul in the moment of death, after explaining the consequences and possibilities to the harmed soul in detail. The mortal can, however, always refuse this option, instead turning into a wraith. If the tem-akh binds itself with a dead soul, they replace the weakest, most flawed part of their soul. The result is a negem-sen, a Saved one, who then undergoes the Hajj, a spiritual journey to the Lands of Faith. Most of the time, the Tem-akh drives the body forward by sheer will, as most souls are too shocked after having to experience the death of their own body in detail to function properly. Then, the tem-akh searches for a group of spellcaster loyal to Osiris that can use the Spell of Life to turn the unliving body of their host into a true Amenti. While the cultists prepare the physical necessities, the soul is guided by Anubis before the Judges of Ma'at. There, their heart is weighed against the feather of Ma'at to determine the worth of the future Amenti. If he succeeds, both the tem-akh and the mortal soul join completely, and the memories and experiences of the tem-akh flow into the mind of the newly created Amenti, as the tem-akh fuses completely with the original host soul.