Ultramarines 4th Company - Invasion of Ultramar: In the meantime, the Warsmith Honsou was consumed by hate for Ventris and the Ultramarines following the events on Medrengard and the destruction of his Chaos Space Marine incubation experiments. He hatched a plan to annihilate the Ultramarines, and especially Uriel Ventris. As bait, he used a stolen Mechanicus virus to turn Tarsis Ultra, the world the Ultramarines had vowed to protect, into a Dead World.He had assembled a large invasion force, which apart from his Iron Warrior warband, included Chaos Cultists, Traitor Marines and Traitor Guardsmen, Drukhari pirates, Kroot and other alien and human mercenaries, a Dark Mechanicum force led by the Traitor Magos Cycerin, and a multitude of criminals, psychopaths and killers.Honsou managed to find and board a star fort hidden for the previous 60 Terran years in the depths of uncharted space in the Ultramar Sub-sector, guarded by an Ultramarines contingent. He slaughtered the star fort's Ultramarines garrison and then freed the powerful Daemon Prince M'kar, secretly held captive within the fort.The daemon, who had once been the Word Bearers Dark Apostle named Maloq Kartho who had originally attacked Ultramar during the Horus Heresy, had been imprisoned by Marneus Calgar, the Chapter Master of the Ultramarines, with the help of the Inquisition.M'kar hated the Ultramarines Chapter and the Imperium of Man with a passion. Aligning with Honsou, the Daemon Prince possessed a desecrated Ultramarine Dreadnought shell so that he could interact with the material universe, turned the star fort into a Chaos abomination linked directly to the Warp, and called forth a huge daemon army to join in attacking the worlds of the Realm of Ultramar.Honsou had managed to acquire a clone of Uriel Ventris, known as the "Newborn," who had been created from the genetic material left behind while Uriel was in the womb of the Daemonculaba on Medrengard. The Newborn was a psychic as well as physical clone of Uriel. As such, he had fragments of Uriel's knowledge and memories, including the defence protocols of Ultramar, which Honsou first used to attack the star fort, and then the entire Realm of Ultramar.The whole Chapter rose in defence of the realm, aided by an Adeptus Mechanicus contingent under Magos Locard, the warband of the system-based Ordo Malleus Inquisitor Suzaku, a squad of Raven Guard Space Marines, the mobilised Ultramaran Planetary Defense Force regiments, and many civilians. The war expanded to encompass several Ultramarran worlds, at least one of which was destroyed. Finally, Uriel confronted the Newborn (and Honsou), on Calth, his planet of birth.Honsou had gone there at the request of M'kar, to the Tomb of Remus Ventanus (an ancient Ultramarine hero of the 4th Company known as "the Savior of Calth") to destroy Ventanus' sarcophagus and his wargear. Uriel killed the Newborn using a blade that was part of Ventanus' wargear, and in the battle that followed Honsou's more numerous force was defeated thanks to the sudden appearance of spectral guardian-warriors.Honsou, faced with capture or death, detonated the explosives the Iron Warriors had previously placed around the tomb, collapsing the grand edifice of the Tomb of Ventanus on top of himself and his opponents. Uriel and some of his fellow warriors survived and headed to Talassar, an Ultramarran world where M'kar and his daemon army were close to overrunning Chapter Master Calgar and his dwindling forces.Uriel and other friendly reinforcements arrived in the midst of the final, climactic battle for the world. Ventris tossed the powerful, anti-daemonic Blade of Ventanus to Calgar as the Chapter Master was duelling with M'kar, and Calgar used it to completely annihilate the Daemon Prince.With the daemon army and Honsou's forces defeated in all the theatres of the war, the Imperial forces proceeded to engage in mopping-up operations, and within six solar months, the Realm of Ultramar was declared free of the touch of Chaos. Ominously, while the ruins of the Tomb of Ventanus were searched thoroughly, the body of Warsmith Honsou was never recovered.