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 strongest 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 soon trusted him enough to give him command of the all of the forces of the Imperium. It is said that he saved the life of the Emperor during the Battle of Reilis when they were surprised. The Emperor repaid this debt when he killed a massive Ork who was threatening the Primarch.