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
The Horus Heresy (novels) Heresy and "Warhammer 40,000" canons; still other non-series Horus Heresy material has been eventually incorporated into the work. A significant development was the 2012 initial release of the "Horus Heresy" miniatures wargame expansion, which repositioned the concept as a foreground element within the "Warhammer 40,000" gaming system while highlighting the importance of the Horus Heresy to Games Workshop's product lineup and the related universe. The expansion is reputedly developed in coordination with the book series, and includes new material and information about the Horus Heresy and the fictional universe; it joins the series and other works as an authoritative source