The Primarch Sanguinius was found on the Planet of Baal by the Emperor. Being the 10th Primarch found he was given command of the 9th Legion the Blood Angels. Sanguinius is known as the "Great Angel", this comes from the angelic set of wings and beautiful appearance of the Primarch. In addition to this out of the Primarchs in terms of combat prowess the "Brightest One" was considered amongst the best in the ways of dueling. 

The Primarch led the Legion with great success capturing whole swaths of space for the Imperium, the Blood Angels practiced hobbies, which was encouraged by the Primarch. The Primarch encouraged this in order for his marines to channel their natural psychic ability and their strong urge to fight and kill. This manifests through a genetic defect in the Blood Angels gene seed. This defect gives the Blood Angels a thirst for blood which can at times become unbearable. 

During the Horus Heresy the Primarch was taken aback by his brothers betrayal. Never the less the Primarch sought out Horus in order to as he put it fulfill his destiny of fighting Horus. Because of this the Primarch died at the hands of his brother which weakened the traitor primarch enough for the Emperor to defeat him in combat. Following his death a defect emerged from the Blood Angel gene seed called the "Black Rage" in which Blood Angel Brothers view themselves through the eyes of their primarch as if they were boarding Horus's ship. This launches them into a Violent frenzy leading to them fighting until they have perished.