Horus image - Sanguinius

Horus (also nicknamed Lupercal) was one of the twenty Primarchs created by the Emperor in the earliest days of the Imperium, just after the end of the Age of Strife. Like the other Primarchs, Horus was sucked from Terra by the Gods of Chaos and was placed on a far-away world in an attempt to prevent the coming of the Age of Imperium.

Horus was the first Primarch to be rediscovered by the Emperor during the early Great Crusade. Because of this early discovery, Horus grew to be the most powerful among the Primarchs as he had grown up from a child to an adult at the side of the Emperor. For a long time he was the only Primarch to have been discovered. Friendship between the Emperor and Horus grew rapidly and the Emperor eventually trusted him enough to give him command of the entire force of the Imperium. The Emperor had saved Horus's life at the siege of Reillis as they fought back to back. At another battle, Horus repaid this debt when he hacked the arm off a frenzied Ork as it tried to choke the life out of the Emperor.

During a mission on the Feral World Davin, Horus was wounded in battle, but the natives of the world helped to heal him.2 Many modern scholars believe that the group of healers were actually Chaos Cultists who somehow managed to take advantage of the illness in the Primarch. After this healing, changes in Horus began to occur. It seems from then on, Horus planned and plotted to overthrow the Emperor in what was to become known as the Horus Heresy.