The Egyptian Book of the dead by P. Le Page Renouf and Edouard Naville

5. _Lord of the One Face_ = μονοπρόσωπος in opposition to πολυπρόσωπος

which is an epithet of the Sky, on account of its many changes of aspect. The Moon too has a variety of phases, whereas the Sun is eminently the “Lord of One Face.” From another point of view the god, at the beginning of chapter 64, is called the “Lord of Two Faces,” the bright and the dark. The Pyramid Texts have the parallel conception of the Two Eyes of Horus, one white and one black, ⁂⁂⁂⁂⁂ (Unas 37).