Celestial Lions - The Mannheim Gap: The Mannheim Gap on Armageddon was a canyon running through the mountains north of Hive Volcanus. It was a rent in Armageddon's priceless earth, torn open by the slow, active dance of the world's tectonics. Any who dwelled there for more than a handful of solar weeks knew that Armageddon was not a world that slept easy, whether due to Greenskins, dust storms, or yet another war.The Celestial Lions were told the canyon had to be assaulted, for it was a nest of mechanical heresy where the aliens were constructing their scrap iron god-machines or Gargants. Hive Volcanus' forces had to strike before the alien Gargants became active, or the tide would forever turn against the city's defenders. The Astra Militarum could not be trusted to deal such a surgical strike, nor could the hive city organise a mass withdrawal and redeployment of its deeply entrenched Guard elements to make it a plausible option. The task fell to the Lions.Primitive Void Shielding protected the site from orbital bombardment. The Lions had to strike overland, without Drop Pods, marching into the ravine alongside their tanks, attacking in battalion regiments like some echo of the Horus Heresy and the millennia of crude warfare before it. The Lions reconnoitred, of course. They scouted and watched, deeming Imperial intelligence reliable. None of the alien god-walkers were infused with life. But time was not on their side. Every solar hour they spent behind their fortress walls was another solar hour that brought the Gargant machines closer to awakening.Five hundred Celestial Lions Astartes attacked. The last half of the Chapter went to war, knowing that the enemy numbers were beyond the capability of the Imperial Guard to confront. They chose to bring overwhelming force and to strike fast and hard, seeking to counter their crippling inability to strike from the skies. Five hundred Space Marines were involved and some Chapters had taken whole worlds with a quarter of that number.The Lion commanders were right to commit their full fury. Any Chapter Master would have done the same. There was no possible way the enemy could have known such a force was coming to destroy them, and there was simply no way to prepare for an assault by five hundred Space Marine warriors. Strike with ferocity and destroy the enemy and then fall back before getting entrenched in a full-scale battle. It should have worked.In truth, the Gargants were not sleeping, they were simply waiting. Despite this setback, if that was all they had to deal with, the Lions might still have fought their way clear without being slaughtered. They might have even won, despite dying to the last man. The Lions' gold battle tanks raged skywards, streams of Lascannon fire bursting thin shields and scoring holes in the hulls of the towering enemy war machines. Warleaders shouted orders, in control of their warriors even in the heat of battle, establishing where to strike, where to push through the Orks' lines, where to move in defence of tank battalions threatened by enemy infantry.Even when the Gargants awoke, the last half of a noble Chapter still fought to win. They would purge the canyon at the cost of their own lives. Dorn himself would have stood with them that day. But the tide truly turned. The enemy ambush unfolded further as Greenskins spilled from the earth, pouring in hordes from warrens within the canyon sides and the rocky ground. There were thousands of them, roaring beneath fanged war banners and standards made from crucified Celestial Lions taken in other battles. This fresh army surged into the ravine, filling it like sand in an hourglass, blocking all hope of withdrawal and eliminating any chance of victory.Somehow the Orks knew that the Lions were coming. There could be no other reason to bury whole war-clans under the rock, waiting for such an assault. Their overlord was a beast clad in scrapwork armour -- the biggest Greenskin the Lions had ever seen. He ate the dead -- his own, and the Lions. Warleader Vularkh buried the war-sword Je'hara in the beast's belly and carved three metres of stinking alien guts free. It did nothing.The Lions fought back as they fell, but they knew they were betrayed. A traitor, somewhere, had fed word to the enemy, and the Orks made the most of their ambush. But soon, the extent of the treachery was revealed, as sniper fire, deadly accurate, rained down from the canyon walls. Not the solid shell rattle of Greenskin projectile throwers, for the Lions knew how the Orks fought. This was viciously precise laser weaponry, knifing through their officers' helms from above. Deathspeakers, Warleaders, Spiritwalkers, even Pride Leaders, cut down with fire too precise, too clinical, to be that of the Greenskin enemy.It took the Lions four solar hours to fight free. They carved their way back the way they came, abandoning a sea of dead tanks, slain Battle-Brothers, and butchered green enemy bodies. The gene-seed of half the Chapter lay rotting at the bottom of that canyon, unharvested by the Lions' Lifebinders and defiled by the thousands of foes they left alive.The Lions had fled from the field, and the most valiant battle the Celestial Lions ever fought was that retreat. Never had they faced such odds, and the last of them cut their way free, pulling their brothers from the storm of blades and fell back to their fortress with the enemy at their heels. The xenos flooded their forward base before most of their survivors had even arrived. The Celestial Lions had to fight just to escape their own falling fortress. Even then, for every gunship that raced free, another two were shot down in flames.The survivors of the Celestial Lions returned to Hive Volcanus. Only three officers were left at dusk of that day, three officers above the rank of Pride Leader. Deathspeaker Julkhara, who called Reclusiarch Merek Grimaldus of the Black Templars brother; Warleader Vakembi, the last surviving Captain of the Chapter; and Lifebinder Kei-Tukh, the Lion's only living Apothecary. The Chapter's future rested on his skills.But the final insult was yet to play out. The last gasp in this drama of shame and treachery occurred later that same, terrible evening. The Lion's territory inside the city was a cold foundry, nearly lightless, with a perimeter of rockcrete patrolled by their remaining warriors.Lifebinder Kei-Tukh did not survive the first night after their terrible defeat. The Lions found him at dawn, slouched against their last Land Raider, shot through the eye-lens. The gene-seed he had carried was gone, and he would harvest no more.The depths of the Celestial Lions' plight on Armageddon were dire indeed: they had lost their fleet, their armoury, their officers and almost all hope of rebuilding their Chapter. They couldn't even cling to pride, after the shame of defeat. All that remained to them was the truth. The Lions vowed to survive long enough to speak it. The Imperium needed to know what had happened to them on Armageddon, where they had been betrayed by others who claimed to serve the Emperor.