Terran Crusade - Amidst the Sea of Storms: Guilliman stepped through the shimmering lights of the Webway gate, enduring the unsettling doubling of reality that it created. He passed from soft illumination into harsh black shadow and searing glare, from air and gentle warmth into the frozen, airless lethality of near-vacuum. Gravity bled away around him, and with a single step, Guilliman launched himself away from the Webway gate into the billowing moon dust beyond.The Terran Crusade had emerged into a deep crater, much of which was immersed in inky blackness. Shafts of stark illumination fell from above, where the rays of Sol itself spilled over the lip of the deep pit. Conscious of the foes following close on their heels, the Loyalists climbed quickly up the pit's sides. Space Marines sprang upwards hand over fist in the low gravity, only one-sixteenth that of Terra.Tanks threw up drifting fans of moon dust as they powered up the rocky slope. Skitarii marched relentlessly upward, ignoring their blackening and freezing organic components. These latter soldiers would not last long on the lunar surface, but they would endure long enough to serve the Omnissiah's needs.Above them, Celestine soared upward into the dark skies -- her Geminae Superia had donned their helms, but the Living Saint had no need of such apparel. Behind them, Veilwalker and her Harlequins lingered by the Webway gate. The Shadowseer gathered her powers, levelling her staff towards the Webway portal and beginning a whispering chant. The runes upon the structure's flanks glowed fiercely with a searing light.Before Veilwalker could finish her ritual, the gate pulsed with dark energies. Blue fire billowed, its roar sounding as a dull rumble in the airless conditions. Veilwalker span clear at the last moment, but many of her Harlequin followers were not so fortunate. Their lithe bodies were engulfed in flame and, as their dathedi suits burned away, so their bodies melted like wax or froze and died.From near the lip of the crater, Guilliman looked back to see the corrupted Webway gate glowing with dark fire. Streamers of energy leapt and coiled, dancing across the walls of the pit and blasting the Eldar corpses to ash. Out from that crackling storm stepped the first Rubric Marines, their footfalls muffled as they advanced across the crater floor. They raised their Bolters and opened fire, cursed shells roaring up from below to slam into the Imperials.Armour ruptured and souls burned. Bulky bodies in the colours of the Novamarines and Mortifactors tumbled in slow motion down the slopes, clouds of chalky dust cascading around them. A Dreadknight toppled backwards, its pilot slain. The remaining Loyalists kept moving, over the lip of the crater and out of the Thousand Sons' line of fire.Here, the retreat stopped at last. Guilliman and his surviving followers stood upon the surface of Luna itself, near the heart of the Mare Tempestus. On every side loomed the rusted hulks of old and broken Imperial voidships, a graveyard of junked and decommissioned spacecraft left there to moulder. Overhead, the blackness of space was speckled with stars while closer to hand, huge orbital docks and defence platforms filled the sky. Gothic leviathans swarming with voidcraft and covered in glaring lights, the grandeur of the Luna docks still faded against the breathtaking sight of Terra itself, hanging stark against the blackness above. There was the destination that Guilliman sought, the end of his journey at last.Yet a deadly foe still chased at the Primarch's heels, and could not be allowed to work his malefic will within sight of the Throneworld. Guilliman knew that the Warp phenomena currently erupting in the crater's depths must surely have triggered every alarm and emergency Augur within a dozen terra-sols.It would not be long before overwhelming Imperial forces raced to investigate, but there was no telling what irrevocable havoc Magnus could cause before they arrived. Guilliman saw again the visions Kairos had sent him, of a shattered world crashing down upon a fire-blackened Terra, and shuddered. He and his followers must hold the enemy here, driving the Thousand Sons back or -- at the least -- keeping them suppressed until aid could arrive.The Thousand Sons were spilling from the Webway gate in increasing numbers, Scarab Occult and Rubricae driven forward by Chaos Sorcerers on their flying discs. Their advance was steady but unstoppable, pushing up the crater walls with their guns blazing. Recognising that the crater itself offered the best chance of containing the foe, Guilliman spread his warriors, combat walkers and tanks around its lip and commanded them to pour fire down into the advancing Thousand Sons.Space Marines, Skitarii, Dreadnoughts, Land Raiders, Vindicators, Dunecrawlers, Battle Servitors and more opened fire. Using the lip of the crater for cover, and making the most of the higher ground, the Loyalists sent volley after volley ripping down into the Heretic Astartes. Striding automata were knocked back into the crater by devastating explosions. Glittering dust drifted from rents in ancient, ornate armour, floating free in the low gravity and leaving once-animate undead armour suits to crumple and collapse.Sergeants barked orders through the Vox, coordinating volleys of Lascannon blasts and Demolisher shells to rain down upon the Rubricae. Cypher and his shadowy companions rained fire down upon the Thousand Sons. Greyfax slammed silver stakes through one Rubricae after another from her Condemnor Bolter. Aldrik Voldus tore Traitors apart with the potent powers of his mind.Armoured corpses piled in heaps at the bottom of the crater, surrounding the Webway gate with carrion remains. From cracks and rocky outcroppings around the crater's edge, the last of the Harlequins added their own fire to the fusillade, hails of monofilament discs cutting through Power Armour and the flesh of living, daemonic discs.For a time, it appeared as though the Thousand Sons would be bottled up in the crater. Though their return fire caused slow attrition amongst the Loyalists, the Traitors were losing far more warriors than they slew.Then a fresh pulse of dark power surged through the Webway gate, its energies whirling faster and faster until they formed a flaming vortex. A wave of supernatural dread swept over the loyalist Space Marines as a huge, hornheaded figure stepped through onto the surface of Luna. Spreading his wings wide, Magnus the Red looked up at Guilliman with a mocking smile.