Before Horus’ treachery was revealed, he sent Sanguinius to a world named Signus Prime to supposedly fight the Xenos known as the Nephilim.
Via our good friends at Lexicanum
Before Horus’ treachery was revealed, he sent Sanguinius to a world named Signus Prime to supposedly fight the Xenos known as the Nephilim. However once in the Signus System the Blood Angels were ambushed by hordes of daemons, and they soon became stranded on the damned world. At the peak of the fighting Sanguinius confronted the Greater Daemon of Khorne Ka’Bandhawho managed to wound Primarch by breaking his legs.
Sanguinius was then rendered comatose by a psychic backlash created by the Ragefire and amplified by the deaths of his sons at the hands of Ka’Bandha. The Red Thirst subsequently erupted across the Blood Angels, and they slaughtered both friend and foe alike in their rampages. Fortunately the Legion Librarians managed to eventually restore the Primarch, and he was able to defeat Ka’Bandha in a second duel, banishing him back to the Warp. Sanguinius then led his forces into the Chaos Fortress on Signus, the Cathedral of the Mark, where he was confronted by the Keeper of Secrets Kyriss the Perverse. Kyriss gave Sanguinius a choice: sacrifice himself to the Ragefire and have the Red Thirst forever lifted from his sons, or allow his Legion to face eventual destruction due to their genetic flaw. Deciding to sacrifice himself, Sanguinius was about to step into the Ragefire when he was beaten to it by Apothecary Meros, who was transformed into the Red Angel. Mourning Meros, Sanguinius slew Kyriss and swore vengeance on Horus.
Reeling from the catastrophe that had befallen him on Signus but determined to defeat Horus, Sanguinius had the Blood Angels set course for Terra. However as a result of the Ruinstorm created by the treacherous Erebus, navigation and communication across the Imperium was made almost impossible. Following the Pharos’ psychic beacon, Sanguinius eventually found his way to Macragge, where Roboute Guilliman, fearing Terra lost, declared a reluctant Sanguinius the new “Emperor Regent” (or Imperator Regis) of his contingency empire Imperium Secundus. Sanguinius was soon plagued by visions of his death at the hands of Horus, and realized this was no omen but a window in the future.
Following the Trial of Curze, Sanguinius, Lion El’Jonson, and Guilliman all agreed to try and breach the Ruinstorm to reach Terra and aid the Emperor who they now knew still lived. Sanguinius was now beginning to suffer from the beginning stages of the Black Rage, which infected Sanguinius’ mind due to the prophetic visions of his own death. In a fit of hysteria Sanguinius nearly struck down one of his own sons aboard the Red Tear. He was desperate to prevent all of his sons from falling as he was, and was seeking any answer.
While in the Ruinstorm, the loyalist fleet came across a variety of horrors and word of an entity spreading destruction known as the “Pilgrim”. During the Battle of Pyrrhan, Sanguinius received a vision and he realized that he needed to go where this struggle had begun, Davin, the world where Horus had fallen. Reluctantly, Guilliman and The Lion agreed to trust in Sanguinius but both had thought they would simply destroy the world upon arriving. At Davin, the loyalist fleet found the entire world surrounded by a shell made of the bones of trillions dubbed the Necrosphere. On Davin, a mass Drop Pod assault was conducted but nothing was found and the population was absent.
The four Primarch’s eventually traveled to the temple where Horus had been subjected to the ritual by Erebus and the Serpent Lodge that had corrupted him. Inside the temple, Sanguinius stood at the altar where Horus had been laid and proclaimed that he would change his destiny. This activated Davin itself, Warp storms roared above and a portal opened up that swallowed up Sanguinius.
Inside the portal on Davin, Sanguinius was back on Terra in a beautiful garden at the Imperial Palace. He for the first time was experiencing a vision that was not his death aboard the Vengeful Spirit. He saw Lorgar dead by his hands and the remaining traitor Primarch’s brought before him in chains. The Emperor congratulated Sanguinius on his victory and named him the Imperator Regis of the Imperium. With Sanguinius as the Emperor’s Regent, he went on to lead a great campaign that purged the Imperium of all corruption and evil and the galaxy was his to rule. Seeing this future and observing the Emperor’s mannerisms, he became suspicious as to what was going on. At last, he cut down the image of the Emperor who was revealed to be the Daemon Madail in disguise.
Sanguinius and Madail engaged in a vicious duel. This resulted in Daemon was impaled by both the Blade Encarmine and Spear of Telesto. The two wounded warriors wrestled with one another until they were both in the portal, torn between the Materium and Immaterium. In the place of where Davin once was, a breach in the Ruinstorm was visible. The path led to Terra, but upon further study it became apparent that somehow Horus had foreseen this route and a large blockade was erected to block them. Guilliman and The Lion agreed to distract the blockade while Sanguinius and the Blood Angels made directly for Terra, for that was their destiny.
n the subsequent Battle of Terra, Sanguinius fought valiantly, organizing the final defence of the Imperial Palace and held the Eternity Gate alone when no others could withstand the horror of the assault, even breaking the back of the same Greater Daemon Ka’Bandha who wounded him on Signum. When the Emperor teleported aboard Horus’s Battle Barge, the Vengeful Spirit, Sanguinius was with him but they became separated and the Primarch was forced to face Horus first. Despite being in the pit of Horus’s tainted and mutated Chaos fueled Battle Barge, Sanguinius tried to revert his brother to the side of the Emperor, using their old friendship as a lever. Horus would not listen to or agree with any of Sanguinius’ words and the two argued and tried to sway the other to the side of the heresy they stood upon. Sanguinius was eventually struck down by Horus, the only damage Sanguinius did was create a small dent in Horus’ armor. Some say, however, that it was through this chink in Horus’s armor that the Emperor was able to deliver the fatal blow. Thus the belief is that Sanguinius did not die in vain; but by dying, allowed Horus to be slain and the Heresy destroyed.
Sanguinius’ body was taken by the Imperial forces as they retreated from the buckling Chaos Barge and his body was borne away to his home planet Baal, where he was laid to rest in the Golden Sarcophagus, deep within a vast tomb whose doors were topped with massive Angel effigies in honor of the fallen Primarch. Of all the Primarchs, Sanguinius is commonly held in the highest honor.
Because he is generally believed to have sacrificed himself to allow Horus, the “Great Betrayer”, to be defeated, the Primarch’s name is cherished by the common citizens of the Imperium. Temples devoted to Sanguinius rise aside those of the Emperor. Sanguinius is commemorated on a sacred day of celebration called the Sanguinala, when adepts across the galaxy wear on their breast the red badge of Sanguinius.