During the Horus Heresy, the Dark Angels were campaigning on the Gordian League shield worlds and were unable to participate directly in the events there.
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During the Horus Heresy, the Dark Angels were far from Terra, campaigning on the Gordian League shield worlds, and were unable to participate directly in the events taking place there. Nonetheless, The Lion was able to lead a small strike force to the Forge World of Diamat, denying traitor forces an important supply base. Once the bulk of the Legion was free from the war against the Gordian League, Warmaster Horus ordered the Night Lords to intercept them on the Eastern Fringe and stop them from aiding the Emperor, but the Dark Angels ambushed and destroyed much of the Night Lords fleet in the Thramas Crusade. During the battle, Night Lords Primarch Konrad Curze became stranded aboard the Dark Angels flagship Invincible Reason, eluding capture and killing every search team sent against him. Following this clash, the Night Lords legion scattered into various raiding parties. These groups would pillage and terrorize the Imperium for the remainder of the war, though at least some would join up with Horus in his drive on Terra. While the Lion hunted Curze himself, the Dark Angels fleet set course for Terra but became lost due to the Ruinstorm.
During their battles against Daemons in the Warp, the Dark Angels violated the Council of Nikea on direct orders from The Lion by reestablishing Librarians. Due to the Warp Storms plaguing the Eastern Fringes the Dark Angels followed the Pharos and moved to Ultramar and joined with Roboute Guilliman and his Ultramarines, helping form the brief Imperium Secundus. During the Lion’s obsessive hunt for Curze, the Dark Angels were used to enforce martial law on Macragge and the Dreadwing hunted the Night Haunter across Ultramar. Meanwhile, another detachment of Dark Angels under Captain Ormand reinforced the Space Wolves against the Alpha Legion at the Alaxxes Nebula while another under Corswain was tasked by The Lion with hunting down Calas Typhon following the Battle of Perditus.
Ultimately after a number of disasters, clashes between Guilliman, Sanguinius, and Lion El’Jonson, and a vision by Sanguinius that the Emperor was alive, Imperium Secundus was abolished. The three Primarch’s led their Legions in an attempt to breach the Ruinstorm and reach Terra. Through an arduous journey, they eventually reached Davin, the nexus of the Ruinstorm, and engaged a vast Daemonic host. After the battle and the destruction of Davin, a way to Terra through the Ruinstorm was clear. However in their way stood many enemy blockades as Horus had foreseen this route. Sanguinius and the Blood Angels raced directly for Terra, as was their destiny, while Guilliman and Lion El’Jonson led the Ultramarines and Dark Angels in diversionary attacks against Horus’ blockade.
The Dark Angels were eventually able to set course for Terra. Their impending arrival, closely following that of the Ultramarines and Space Wolves legions, (who had overcome similar obstacles), forced Horus to gamble everything on a duel with the Emperor, his former master. Horus was defeated by the Emperor, although the Emperor himself was fatally wounded and had to be entombed within the life-preserving mechanism of the Golden Throne. El’Jonson was stricken with grief over the fact that he had not been able to protect the Emperor against Horus. After the Heresy, the Dark Angels helped restore order to the Imperium. However, during this time, the Dark Angels who had been left behind on Caliban became agitated at being forced to essentially babysit a backwater planet. This led to the leader of the garrison, Luther, turning to the Gods of Chaos, who had just been defeated with the death of their champion Horus during the Heresy.
Read More About The Dark Angels During the Horus Heresy
