Fallen Angels (Novel) - On Diamat: Meanwhile, across the galaxy, in the two hundredth standard year of the Great Crusade, Lion El'Jonson and his Dark Angels prepared to assault the Forge World of Diamat.Having heard of Horus' rebellion against the Emperor, the Lion, primarch of the Dark Angels, set a plan in motion to cut off Horus' ability to lay siege to Terra. Having learned of incredibly powerful Titan-like siege engines built in secret on Diamat by the Mechanicum, Johnson diverts a strike force of 200 Dark Angels Astartes to Diamat with orders to secure them.However, he only tells his Astartes that Diamat must be secured to keep the incredible production power of Diamat out of the rebel Warmaster's hands. The Lion knows that time is of the essence; a huge strike force of Astartes is headed to Isstvan V to deal with Horus' betrayal. The Lion believes that Horus will try to secure the siege engines quickly and consolidate them on Isstvan.Brother-Redemptor Nemiel, now a Chaplain, is chosen for the mission to Diamat. Nemiel had distinguished himself in a campaign against the Orks, rallying his brothers and serving as the source of inspiration that carried the day.The Dark Angels strike force makes it to Diamat in the middle of a rebellion against the Loyalist Mechanicum led by the Hereteks of the Dark Mechanicum. The Dark Angels' fleet is severely crippled and a group of Astartes are sent to the surface to secure the forge cities.Ultimately, Nemiel and his squad uncover the treachery of the Dark Mechanicum forces on Diamat, independently discover the siege engines, and secure the warehouse containing them.In the ensuing betrayal by the Dark Mechanicum forces, nearly all of the Astartes and their fleet are wiped out. The Lion joins Nemiel in the warehouse with the survivors, believing that they would be safe there from bombardment by sheltering amidst the extremely valuable siege engines. The Astartes are unable to unleash the siege engines themselves because there are no manual controls, as the Dark Mechanicum had prepared them to be used by their allies in the Warp.However, the Dark Angels are able to gain control of one of the siege engines by transplanting Brother Titus from his Dreadnought sarcophagus into the siege engine.The Sons of Horus arrive, and together with the rebel Dark Mechanicum forces on Diamat, assault the Dark Angels, but are repelled by Brother Titus controlling the siege engine. Out of time to complete their mission, the Sons of Horus retreat from the planet.After the planet is secured by the Loyalists, the Lion converses with Perturabo, the primarch of the Iron Warriors Legion, who was stopping at Diamat to refit on his way to "deal" with the Traitors at Isstvan V. The Lion did not appear to suspect that Perturabo had already sworn his loyalty to Horus.The Lion asks Perturabo to keep his involvement on Diamat a secret, saying: "I wouldn't want the Emperor to believe I did any of this with an ulterior motive in mind."The Lion expresses his belief that Horus was chosen as the Warmaster only because he was the first primarch found, and that if he had been found first, he would have been the Warmaster.The Lion asks Perturabo to support him for Warmaster when the Emperor chooses Horus' replacement. Perturabo agrees to do so.And with that, the Lion gives Perturabo the siege engines for use against the Traitors on Isstvan V, never realizing that they will be used against the LOyalists in the greatest betrayal in Human history at the Drop Site Massacre not long after.