Second Battle of Davin
The Second Battle of Davin was a battle during the Horus Heresy.
Following the dissolution of Imperium Secundus the three Primarch's within Ultramar, Roboute Guilliman, Sanguinius, and Lion El'Jonson, attempted to journey to Terra and aid the Emperor against Horus. However to do so they would have to move their fleets through the Ruinstorm, a feat considered near-impossible. Nonetheless 2/3rds of the Ultramarines, Blood Angels, and Dark Angels departed Ultramar and set course for Terra. After many weeks of ineffectual Warp jumps that even Lion El'Jonson's Tuchulcha had difficulty navigating, The Ultramarines came into possession of several Chaos-corrupted Navigators after the Battle of Anuari. Unlike their loyalist counterparts, traitor Navigators had far less difficulty navigating the Warp and were surprisingly quite eager to lead the loyalist fleet through the Ruinstorm.
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. A bombardment managed to penetrate the sphere and the fleet was soon in orbit above Davin. While over Davin, Sanguinius shocked The Lion by boarding the Invincible Reason and taking the captive Konrad Curze with him. Sanguinius hoped to use Curze's prophetic abilities to determine what he was meant to do upon Davin. Sanguinius then commended a mass landing on the world, and the enraged Lion nearly ordered that Davin be subjected to Exterminatus regardless of Sanguinius' presence on it. At the last minute The Lion relented, and realizing how close he had come to committing a great sin followed Sanguinius onto Davin with his Dark Angels along with Guilliman's forces.
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. Guilliman and The Lion desperately tried to penetrate the portal, and the chained Curze broke down as he had not foreseen anything that was transpiring and his worldview that destiny was set in stone was being tested. Above Davin, the orbiting loyalist fleet was assailed by a a fleet of Daemonships that appeared from nowhere. All the vessels were Imperial ships previously thought lost in the Warp, but had since become twisted by the powers of Chaos. At the fleet's head was the Veritas Ferrum, which had grown far beyond its original size and was horrifically mutated. The Veritas Ferrum announced its arrival by instantly destroying the Iron Hands Cruiser Sthenelus.
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.
At the revelation of the presence of Madail, Daemons began to appear across Davin's surface and assaulted the Space Marines guarding Guilliman and The Lion, who were still attempting to breach the portal while Curze despaired at his blindness to the future. In space, the battle was going poorly. Every ship struck down by the Daemonic fleet was reborn as a twisted husk and another of its number. The Veritas Ferrum proved near-invincible, not only blasting vessels with Warp-fire but swallowing them whole in with massive jaws. Guilliman's flagship, the Samothrace, was destroyed when it delivered Cyclonic Torpedoes at point-blank to the Veritas Ferrum. To the horror of the Imperials, the Daemonic ship survived the blast and quickly regenerated. It seemed that the vessel could not be stopped.
Inside Davin's portal, Sanguinius and Madail engaged in a vicious duel. Madail had unleashed a Daemonic horde through the portal to prevent Guilliman and The Lion breaking through. The host included a massive Soul Grinder, which was destroyed in a combined effort by The Lion and Guilliman. On the other side of the portal, The Angel was eventually pinned by Madail's host of Daemonic troops, and the Preacher of Chaos Undivided announced that Sanguinius would serve or die. Madail dubbed Horus an imperfect vessel, and urged Sanguinius to strike Lupercal down and take up the mantle as Warmaster of Chaos. If he did so, Madail declared, his sons would be spared of the Black Rage. However despite the temptation Sanguinius denied the Daemon and broke free of his captors. Sanguinius and Madail again engaged in a duel, but this time the 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. On Davin, Guilliman and The Lion saw Sanguinius' upper half sticking through the portal and rushed to his aid, but were blocked by Daemons. The stalemate endured, until Sanguinius' Herald stepped forth and declared that he would take The Angel's place in the portal. Realizing that this was his herald's destiny and that he needed to confront Horus at Terra for the Imperium to endure, Sanguinius solemnly agreed. The Sanguinor charged into Madail, and as he tackled the Daemon back through the portal was transformed into a golden angelic form. The Primarch's and their escorts managed to escape the Temple just as it collapsed.
However, the defeat of Madail did not stop the Daemonic incursion on Davin. The Veritas Ferrum and its escorts still battered the Imperial fleet and the Space Marines on Davin's surface were under assault from vast hordes of Daemons. The three Primarch's managed to conduct an evacuation from Davin, and once aboard the Red Tear knew that Davin was linked to the materialization of the Veritas. Davin was bombarded with Cyclonic Torpdoes, and with its death the Veritas Ferrum and its Daemonic fleet vanished.
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. Sanguinius took Curze with him, stating he would face their fathers justice, though in truth he would put the Night Lords Primarch into a stasis coffin and inject him into space.
The arrival of the Blood Angels to Terra proved instrumental in the upcoming siege, with Sanguinius infamously dying by the hands of Horus aboard the Vengeful Spirit. In addition, the destruction of Davin proved to have a weakening effect on the Ruinstorm, which began to dissipate after the battle.