MG9/9

Hermes says:
"Yes, they were 9, the Ennead: Atum, his children Shu and Tefnut, Ra, Nut, their children Osiris and his wife Isis, Seth and his wife Nephtis.
Yes, they were endogamic, by the way... Now the question:
Who was the name of the pharaoh who invented monotheism in Egypt?
*Mummrah
*Tutankhamon
*Horemheb
*Amenophis IV
Click MG9? for hint