Roboute Guilliman - Second Battle of Davin: Following the Trial of Konrad Curze, Sanguinius, Lion El'Jonson, and Guilliman all agreed that the Imperium Secundus had been a mistake and should be disbanded. Instead, they agreed to try and breach the Ruinstorm to reach Terra and aid the Emperor, who they had learned still lived, in the defence of Terra from Horus.As they sought to navigate the Ruinstorm, the combined Loyalist fleet of Ultramarines, Dark Angels and Blood Angels came across a variety of horrors and word of an entity spreading destruction across the galaxy known as the "Pilgrim." During the voyage through the Ruinstorm, Guilliman's fleet was ambushed by Traitor forces at Anuari, where Guilliman survived an assassination attempt by the Word Bearers armed with the Chaos blades known as Athames.Believing he could study the weapons to gain a better understanding of Chaos and potentially use such knowledge against the Traitors, Guilliman kept the blades in his vault.During the Battle of Pyrrhan, Guilliman commanded the Ultramarines personally while Sanguinius received a vision and realised that the fleet needed to go where the Horus Heresy had truly first begun, the cursed world of Davin. Reluctantly, Guilliman and Lion El'Jonson agreed to trust in Sanguinius despite their skepticism of his vision, but both had thought they would simply destroy the world upon arriving.After arriving in orbit of Davin, Sanguinius shocked El'Jonson by boarding the Dark Angels flagship Invincible Reason and taking the captive Konrad Curze with him. Sanguinius hoped to use Curze's known psychic precognitive abilities to determine what he was meant to do upon Davin. Sanguinius commanded a mass landing on the world, and the enraged El'Jonson nearly ordered that Davin be subjected to Exterminatus regardless of Sanguinius' presence on it.Brought back to his senses before such a horrific betryal could occur, a chastened El'Jonson explained to Guilliman that he believed something was trying to manipulate them begin walking the path of damnation like Horus and the other Traitor primarchs. Convinced that his brother was correct, the Ultramarine primarch realised the source of the corruption. Guilliman retreated to his vault, and crushed the captured Athames with his Power Fist even as he declared to the Dark Gods that he would not be tempted as Horus had.On Davin, Sanguinius was trapped within a Warp portal and did battle with the daemon Madail while Guilliman and El'Jonson desperately tried to reach him. A vicious battle erupted both on Davin and above it, in which Guilliman's acting flagship Samothrace was destroyed by the Daemonship Veritas Ferrum.During the battle that erupted at Davin's Temple of the Serpent Lodge, the place where Horus had been corrupted by Chaos, Guilliman and El'Jonson finally managed to put aside their lingering emnity and fight together as brothers should, defeating a massive Soul Grinder.Eventually, Sanguinius was able to escape from the Warp and the Space Marine forces evacuated the world to orbit. Davin was destroyed by Cyclonic Torpedoes, and with its anchor in realspace gone, the daemonic fleet which had protected the world vanished.Left behind in the space where Davin had been a breach in the Ruinstorm became visible to the combined fleet. The path through led to Terra, but upon further study it became apparent that somehow Horus had foreseen that this route to the Throneworld would open and he had left behind a massive fleet of Traitor warships to prevent the passage of the Loyalist fleet through that route.Guilliman and El'Jonson agreed tthat the Ultramarines and Dark Angels fleets would face the Traitors while Sanguinius and the Blood Angels slipped through the breach in the Ruinstorm and made directly for Terra, for that was their destiny as predicted by Sanguinius' visions of the future. If the Blood Angels did not make it to the Throneworld, the Traitors would claim final victory.The plan proved successful, and in the solar months that followed, the Ruinstorm began to dissipate, allowing easier travel through the Warp. Guilliman gathered whatever Ultramarine forces he could and at last began to make his way to Terra.In his path lay a large defensive chain of hundreds of worlds manned by the Iron Warriors. In a series of bitter engagements, both sides took heavy losses but the Ultramarines were able to maintain a slow and painful advance on the Throneworld.Ultimately, Guilliman was able to set a final course for Terra. Travelling at maximum speed, his Legion was only solar hours away when the final battle of the Siege of Terra began aboard the Warmaster Horus' flagship Vengeful Spirit.