Horus as bright as the sun was explained by a tale, known as "The Contendings of Horus and Seth". In this tale, it was said that Set, the patron of Upper Egypt, and Horus, the patron of Lower Egypt, had battled for Egypt brutally, with neither side victorious, until eventually the gods sided with Horus. As Horus was the ultimate victor he became known as "ḥr.w wr" "Horus the Great", but more usually translated "Horus the Elder". In the struggle, Set had lost a testicle, and Horus's eye was gouged out. Horus represented the eclipsing binary Algol in the Calendar of
Horus Heresy (fictional event) ceremony designed to heal Horus of a mortal wound, he is shown a vision of the far future, in which the Emperor is worshiped as a god, and Horus and the other Primarchs are forgotten (The irony being the Heresy is what leads to this future). As the Emperor's primary edict is to stamp out religion in all forms, Horus sees this as the ultimate betrayal. Though another Primarch, his brother Magnus, tries to reach the Emperor by psychic projection and warn him of Horus' treachery during his trance like state, the corruption spreads and prevents Horus from accepting his