Dark Angels - Second Battle of Davin: In the wake of these revelations, Imperium Secundus was abolished by the three primarchs as an unfortunate mistake. The three primarchs led their Legions in an attempt to breach the Ruinstorm and reach Terra to defend the Emperor now that they knew He still lived.Once in the Ruinstorm, the combined Loyalist fleet came across a variety of Warp-born horrors and word of an entity spreading destruction known as the "Pilgrim". Not even the Tuchulcha Engine proved capable of navigating the Ruinstorm, which frustrated the Lion. During the Battle of Pyrrhan, El'Jonson commanded Dark Angels Astartes as Sanguinius received a vision and realised that he needed to go where the Horus Heresy had truly begun, the world of Davin.Through an arduous journey, they eventually reached Davin, the nexus of the continuing Ruinstorm in realspace, and engaged a vast Daemonic host on and above the world in what would be remembered as the Second Battle of Davin.Reluctantly, Roboute Guilliman and the Lion agreed to trust in Sanguinius but both had thought to simply destroy the hated world upon arriving from orbit. After the fleet emerged over Davin, Sanguinius shocked El'Jonson by boarding the Invincible Reason and taking the still-captive Konrad Curze with him.Sanguinius hoped to use Curze's prophetic abilities to determine what he was meant to do upon Davin that could helpt to save the Emperor. Sanguinius commanded a mass ground assault on the world, and the enraged Lion nearly ordered that Davin be subjected to an Exterminatus action regardless of Sanguinius' presence upon it. At the last moment El'Jonson relented, and was immediately horrified by what he had nearly done. He realised that some external power was attempting to force the primarchs down the path to damnation, and he followed Sanguinius down to the surface of Davin.On that dusty world, Sanguinius was trapped within a portal to the Warp and did battle with the Daemon Madail while Guilliman and the Lion desperately tried to reach him. A vicious battle erupted both on Davin and above it in the void, where Guilliman's acting flagship Samothrace was destroyed in orbit by the Daemonship Veritas Ferrum.During the ground battle at Davin's infamous Temple of the Serpent Lodge, where Horus had first been corrupted by Chaos, Guilliman and El'Jonson managed to finally fight as partners and brothers. Together they brought down a massive Soul Grinder Daemon Engine.Eventually, Sanguinius was able to escape 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 vanished back into the Empyrean and where Davin had once been, a breach in the Ruinstorm was now visible. The path though led directly to Terra, but upon further study it became apparent that Horus had foreseen that this route to Terra might open for the Loyalists and had blocked it with a gauntlet of multiple Traitor fleets. Guilliman and the Lion agreed to distract the blockade while Sanguinius and the Blood Angels fleet made directly for Terra, for that was their destiny.Sanguinius and the Blood Angels fleet then raced directly for Terra through the opening, as was their destiny in Sanguinius' precognitive visions, while Guilliman and Lion El'Jonson led the Ultramarines and Dark Angels Legions in diversionary attacks against the Traitor fleets that allowed the Blood Angels to slip through the cordon.By the time the Siege of Terra began, the Lion hoped to draw Traitor forces away from the Throneworld by striking at their own Legion homeworlds. As a result, the Dark Angels destroyed several Traitor homeworlds such as Chemos of the Emperor's Children and Barbarus of the Death Guard, acts that the Lion would come to relish.