Long, long ago, the Egyptians created a kind of magical technology to prevent their souls being bound to their bodies. They called it 'mummification'. The worshippers of Aten, forever looking to pervert the traditional way of doing things, created 'anti-mummies'. Their bodies were converted into terrible magnets for the spirits of death, drains into the dark spirit world. The Aten Mummies are filled with former cultists' spirits, funnelled from their afterlives into the heavily treated corpses of their former lives.
These acolytes called The Hand of Aten are what passed for success stories in the Aten cult's necromancy: in their early unlife, their flesh remained wet and warm to touch, and their eyes burned with the hateful intelligence of a single occupant. Having renounced the afterlife, these immortal cultists were neither living nor dead, but at some cursed in between. Sorcerers of note in life, their time in the beyond had taught them further dark arts, and on their return they drank of the Filth to learn its ways. Utterly devoted to their king, they remained at his side even after he became too vile for his human subjects to stomach audience with, attending his megalomaniac decrees.
After centuries of biding their time below the baking desert heat, they have returned to take their place as his honour guard - his most faithful, the Ones Who Waited - hands and faces still blackened with the touch of the Filth.