Horemshep was an Egyptian priest who discovered a stasis box that had fallen to Earth. Upon opening it, he discovered its occupant, a being of pure thought that could possess people's minds. He then purposed to use the entity to overwhelm his enemies through the entity's possession.
Chief in his sights was Erimem, a young female who stood to be crowned Pharaoh, and her mentor, the chief of the royal guard, Antranak. He and his military ally Yanis cooked up an alternate royal succession and gathered an army of mercenaries to make it happen.
Ultimately, the Fifth Doctor and Erimem were able to contain the priest's stasis box entity, and in so doing to fully reveal Horemshep as a villain. Though he tried to claim possession by the entity, Erimem did not believe him, and ordered Antranak to carry him back to Thebes in chains. (AUDIO: The Eye of the Scorpion)