Finally, growing tired of watching, the Primarch entered the battle from above, tearing the sky and leaking the essence of the Warp into realspace!
Via our good friends at Lexicanum
Ahriman pulled everyone back further, to the final line in front of the Pyramid of Photep. Briefly having won time to assess his forces, the Chief Librarian realised barely 1,500 Sons still lived, and the Pyramid was crammed full with the surviving citizenry, last survivors of a lineage of scholars that descended from Old Night. With the narrower perimeter and such heavy cover, the Sons were able to briefly hold off the resurgent Space Wolves before the Wolves unleashed their terror troops, figures that the Thousand Sons at first thought were giant wolves, and then realised were part-armoured marines. The Wulfen burst into the Thousand Sons’ lines, causing havoc and many deaths. With the approaching howl of Leman Russ himself echoing in their ears, Ahriman and all the others prepared to meet their deaths.
This however, would not come to pass. For Magnus, watching all the while, finally decided to enter the battle. No longer able to watch the slaughter of his children and destruction of his works, Magnus descended from the Pyramid of Photep with lighting, fire and rain, slaying the Wulfen explosively and driving the Space Wolves back with the ferocity of the deluge, spearing them with telekinetically flung shards of glass, slaying them with one baleful gaze of his eye, and detonating their armoured vehicles with bolts of energy from his staff. From where Magnus descended, the sky split asunder, the very essence of the Warp leaking into realspace.
Hundreds of eyes gazed down from this crack in space/time, driving any who gazed back at them insane. As the Space Wolves pulled back before Magnus’s overwhelming display of power, only Leman Russ and his two wolf companions, (presumably Freki and Geri) stood unmoved. As Magnus made to confront the Wolf King on the causeway before his pyramid, he slowed time enough to issue his last order to Ahzek Ahriman, that his Chief Librarian and most gifted student retreat inside the Pyramid and report to Amon, his Equerry, in order to receive guardianship of the Book of Magnus. Magnus had foreseen that Ahriman would survive the day, but believed himself destined to fall. With that, the Crimson King engaged Leman Russ in personal combat.
Magnus generated a lighting cage around them, so that no allies could disturb them, before blasting his brother with such energy. Apparently immune to such attacks, Russ closed with the Red Cyclops, striking enough blows on him that his breastplate cracked open. Staggering back, Magnus hit Russ with a blast of balefire that cracked his own armour and set light to his hair. Separated back out to weapons’ length, frostblade met golden axe, as the two combatants duelled with each other. To all those watching, lit by lightning, drenched by bloody rain and each impact echoing with the thunder, the two kings seemed to swell with power and become as if giants.
At this time, in the nearby ruined halls of one of the cult pyramids, the Space Wolf Skjald Kaspar Ansbach Hawser found himself confronting his own personal daemon, an agent of the entity that had crafted his life for the very purpose of helping create the current events. After a tense stand-off, the daemon attempted to slay Hawser, but Hawser was saved by the intervention of several Space Wolves and a detachment of Sisters of Silence.
Back at the central battle, the rallied Adeptus Custodes and Space Wolves forces sought to circumvent the duel and enter the Pyramid, crashing across the moat in their eagerness. Magnus spotted this and with one gesture turned the moat to bubbling acid, slaying or wounding all those caught within it. Shadowy hands formed out of pools of standing water on the ground, reaching for those who returned to the moat or stayed on the edge, the wounded dragged down into the dark. As the warpstorm in the sky continued to manifest, the earth shook and split, and it seemed as if Prospero and all upon her were damned.
In the centre of it all, Magnus and the Russ continued to fight, Magnus battering the Wolf King with fists wreathed in lightning and fire. One of Magnus’s mighty fists clove into Russ’s chestplate above his heart, the attempted death-punch shattering it and sending ceramite shards deep into his body. Russ grabbed the offending arm and snapped it like a branch. Magnus speared his brother with a blade of pure thought formed around his other hand. As Magnus held his brother transfixed and prepared to finish him off, the two wolf companions of the Primarch leaped at the legs of the Crimson King, sinking their jaws into his flesh.
Staggering back, Magnus dissipated the thought-blade, slamming his fist into the head of the black-furred wolf, bursting apart its skull and dropping it to the ground. Roaring in frustrated anger and pain, he grabbed the white-furred wolf with a thought and flung it far over the heads of the watching Space Wolves before turning back to his brother. The two wounded primarchs returned to their wrestling match, somehow levitating over the causeway.
Now distracted by the combat, Magnus was unable to prevent a second wave of Wulfen from dashing through the moat, supported by groups of Space Wolves using shards of the pyramid and the stocks of their bolters to make improvised canoes. As Ahriman tried to concentrate enough to direct a force to fight off these approaching threats, a roar of agony from above, followed by a second, separate, louder one directed all attention upwards. Magnus had struck Leman Russ with a particuarly concentrated sorcerous attack, wounding the Wolf King again, but causing him to lash out randomly with his blade in response.
The tip of the blade swept across Magnus’s remaining eye. In the instant after Magnus reeled from this blow, all the extraordinary pyrotechnic effects surrounding the duel vanished, including the impression that both combatants were giants. leaving all to see two brothers standing staggered and in pain upon a simple causeway. Grievously hurt, Magnus called on regenerative magic to heal his arm and eye, but Leman Russ grabbed him, lifted him high, and broke his back across his knee. The sound echoed like a gunshot in the heart of every watching Thousand Son. As Magnus fell to the ground and the sky wept oily tears for his fall, Magnus mind-linked with Ahriman and revealed his last gift. As Russ brought his frostblade Mjalnar down in a fatal arc, Magnus used Ahriman as a conduit to enact the last part of a great master-spell he had prepared. With those words of power, Magnus and all the Thousand Sons instantly vanished from the surface of Prospero. Mjalnar smote the ground where Magnus had lain.
The Space Wolves had won, but the Thousand Sons had escaped execution.
