 Sacrifice can be a noble thing indeed. The surrender of the self, be it in effort or even life for the cause of another, is the ultimate in selfless acts, the sublimation of the one for the sake of the many. A virtue indeed, but one that must be carefully acknowledged and checked should the tendency towards sacrifice become too strong. The pathology that is created is ultimately detrimental to all. Couched in painfully blunt economic terms, the coin of sacrifice must be spent well for the benefit of the many rather than the simple satisfaction of the self's obsession. Such fixations are drawn from sundry experiences and myths as diverse in their nature and pedigrees as the stars in the sky. The following chronicle details the birth of such an obsession, of an engagement so selfless it became enshrined into not only Astartes legion, but imperial myth. No then, that this is the record of the penultimate ground conflict of the unification wars, the clash between the ancient and the modern, and the birth of something altogether new. A record of the assault on the Tempest Galleries by the 18th Legion Astartes. While it is highly likely that the 18th Legion took place in combat operations prior to the engagement that is the subject of this record, this is unverifiable in available historiography. The records could simply have been lost with the grinding passage of time, or the heavy hand of imperial redactionism, or perhaps simply been expressly sealed by the writ of the highest authorities. The 18th Legion was a member of the so-called tree foil of Astartes legions, alongside the 6th and the 20th. Legions selected it is said personally by the emperor for some express but unknown purposes from the beginning of their initial alpha induction phase. The purposes are of course unknown to scholarship. Every Legion created fulfilled specific battlefield roles, and all would go on to lead storied and renowned, infamously or otherwise, histories. The legions of the tree foil were no exception, but there is not to connect them beyond this half-rumored designation, and the unusual level of secrecy that veils their conduct during the unification wars, and even, laterally, the solar reclamation. They are as unlike a trio of legions as it is possible to select, even by the diverse standards of the Legion Astartes. There is certainly next no record in historiography of any special coordination of each during the long years of crusade that would follow humanity's conquest of its birth system. What we are instead left with, as with so much born of this time, are questions, lingering and persistent. We are left instead to pick apart what records we have in search of answers likely unanswerable, and in this, historiators such as yours truly must persist. The Tempest Gallery assault is, once again, the first verifiable engagement involving the 18th Legion in the Chronicles of the Imperium, and, though it was to occur decades before the Legion was reunited with its Primarch, Vulcan, to rechristen themselves with their new Cognamen of the Salamanders. The battle was nevertheless to have a seismic effect on their history, and more importantly, their character. The assault on the Tempest Galleries was one of the last full-scale engagements of the period of Terran history known as the Unification Wars, the global conflicts that marked the birth of the Imperium, with the Emperor himself leading his Thunder legions, and later Astartes legions, in a grand push to subjugate and unify the human homeworld under his rule. The bloodshed and the devastation were hitherto unseen, even for the war-ravaged planet, but they were, at this point, beginning to draw to a close. The Caucasus wastes were the last grand geographic holdout, a region that had stubbornly and violently resisted all attempts to bring them under the lightning and raptor banner of Imperial unity. A full-scale invasion was the only recourse, but it would prove no simple task. The eugenicist oligarchs that controlled the wastes possessed some of the most potent relic technology extant on Terra, a force-multiplying factor that made them inordinately more challenging opponents than the comparatively vast numbers defeated in the Indonesian bloc or the mountains of Ursh. The technology was pre-Age of Strife in origin, devices and systems created in the depths of the Dark Age of Technology, which the oligarchs wielded with nigh abandon in the mad rule of their realms. The reckless genetic augmentation processes had granted them armies of so-called Urukassis, armoured and enhanced soldiery that were, in effect, the equals of the Emperor's own thunder warriors, supported as they were upon the battlefield by device-thralled, narcotically dependent covens of human psychers. The ethnarchy, as this regime was globally known, were ensconced within subterranean fortresses buried in the mountain ranges of the Caucasus wastes, their technology granting them multiple layers of redundant energy shielding, protecting them from external bombardment. An earlier imperial invasion in the Unification Wars, a full-on storm assault against these fortresses by the Legio Cataegis, had resulted in them losing nearly 10,000 of their thunder warriors, alongside approximately one million baseline human casualties from regiments of the Old Hundred. With such staggering losses, and less dangerous regimes still opposing him, the Emperor cordoned the wastes off, subjecting them to a withdrawn but protracted siege that, unfortunately, did nothing to diminish the ethnarchy's self-sustaining potency. The final assault on the wastes saw the mustering of six proto-legions of Astartes in their entirety, the first time so many legions had been wielded against a single foe. Supplementing them were the majority of the Emperor's life wards, the Legio Castodis, for the master of mankind himself was to take to the battlefield. Behind his banners were countless armies drawn from his realms and satrapies, and mercenary bands following the Imperial Raptor for coin and plunder. It was as mighty a host as had ever been assembled upon the homeworld, an army to sunder the final, vile fortresses of a cancerous regime born of the worst darknesses of the Age of Strife. But the first thrust, as it were, was to be entrusted to the newly raised 18th Legion Astartes. The decision was questioned by many, including senior officers from the regiments of the Old Hundred, as well as the ever suspicious tribunes of the Custodians. So inexperienced and so essentially unproven an asset as the 18th Legion should surely not be entrusted with so vital a role in what was assured to be a supremely costly invasion. The Emperor was adamant, however, that the 18th were the Legion for the task, and his writ, as ever, could not possibly be countermanded. The Legion would be committed to their task via the use of termite pattern assault drills, a subterranean transport vehicle newly offered to Imperial use thanks to carefully arranged technology exchanges with the then still mysterious Mechanicum of Mars. The Legion numbered approximately 20,000 Astartes at this juncture, and this force, in its totality, was assigned to assault the geothermal power plants that provided the energy needed to maintain the ethnarchy's shield technology. These were the Tempest Galleries, a nigh legendary string of caverns, some 100 kilometers in length running below the wastes. So called for the electromagnetic storms and flame cascades, the ancient power-generating machinery would cause with its very operation. The mission was vital and supremely dangerous. Notwithstanding the aforementioned lethal storm systems within the caves, Imperial intelligence was based on centuries old data and fragmented geo-imaging scans. The full layout of the galleries was completely unknown, as was their number, composition, and even the existence of potential enemy elements defending them. Finally, even the termite pattern drills were hitherto untested, their efficacy a thing of Martian promises and little else. In spite of all of this, the 18th Legion, clad in specially camouflaged power armor of black and sulfuric yellow stripes, pledged themselves to the cause before the Emperor himself and committed to the task at hand. Contact was rapidly lost, as the assault drills dug deep into the crust of Terra. The Tempest Galleries, located below even the depths of the ethnarchy's fortresses themselves, were expected to be beyond the range of even the most powerful Voxcaster. But the Emperor's own bonded Psyker prognosticators found that their sights were shrouded. The fate of the 18th Legion would be unknowable to the hosts of unity from this point onwards. The Emperor's hosts were placed at full battle readiness, but the hours dragged on and on and on. The 18th detractors once again came before their King, to question him for guidance, to reason that surely the assault was reckless and that an attack must be mounted before the ethnarchy could strengthen their defenses further. The master of mankind would only rebuke their petitions, stating that his Legion would not fail him, that they would return from the fire and thus it shall ever be. Below them, the 18th Legion ground onwards to their targets. Some 20% of their number simply died during the transit. Environmental hazards claimed them. They were ground to dust and meat paste, being caught amidst tectonic plates, or pulverized by mineral stream cave-ins. They were incinerated in magma flows, victims of molten rock overwhelming the shields of their Martian transports. But, breach the Tempest Galleries they did, forcing themselves through the cavern walls, bringing them into an utterly alien landscape. Kilometre high machinery turned overhead, suspended over oceans of boiling magma, suffusing expansive silicate webbing with crackling, barely contained electric power. It was, rapidly, discovered that in this airless furnace, this cathonic hellscape, there were no ethnarchy soldiery. No human had set foot in this lethal unplace for millennia. The power engines were born of the dark age of technology. Their systems were so immaculately refined, their constructions so robust, that thousands of years of ceaseless function had not diminished their output one iota, nor the potency of their defenders. For defenders they had, service automata, machine intelligences, likewise born of the dark age, their metallic hides blackened by their infernal domain, but no less intact. Like antibodies reacting to a virus, they set upon the 18th Legion immediately. Previously, unneeded defensive algorithmica activated the second intruders breached their sovereign domain. Each had been built with forgotten technology to survive millennia of servitude in extremely exacting environments. Had they been pitted against the battle automata of the Mechanicum, each would have reaped dozens of Martian machines before being brought down. There were, contained within the Tempest Gallery, thousands. Plasma and Melter weapons barely scorched them, for they had been created to work within magma itself. Bolt around slid off their surfaces like rain off waterfowl. The one combat solution was massive sustained kinetic force applied to their relatively vulnerable joints, disabling movement. This lesson was dearly bought, costing the 18th Legion hundreds of Astartes. Running battles against swarming automata rapidly became the layout of the battle. Defending the termite drills became untenable, as these were now the target of far vaster automata, spherical mechanical beasts with toothed maws used by the Tempest Gallery systems to expand and maintain their magma tunnels. Only a mixture of transhuman resilience and suicidal fury served to maintain both unit coherency and dogged resistance against a foe. Everywhere, individual battle brothers would hurl themselves at a partially downed automata, reasoning that the coin of their lives could now be sold to preserve those of their kin. A grim arithmetic of death. The assault rapidly became less about objectives and now about mere survival. Shorn of the potentially defensible positions of their incursion points, units of the 18th moved from gallery to gallery with whatever coherence they could manage, collapsing tunnels to buy time and hopefully trap their mechanical foes. Thousands of casualties had been sustained as the battle progressed into the twelfth hour. The sacrifice of so many Astartes in suicidal runs on the enemy, having bought their surviving brothers enough time to not merely coalesce forces of arms, but to crucially adapt. Displaying a caniness for technology and field craft that would become the defining trait of the salamanders, the nascent 18th Legion scavenged and salvaged the machinery around them, and that of former automata drones, to augment their own war gear. As the battle progressed, so too did the 18th's familiarity with the systems around them. For all the advancement of the dark age of technology, the devices were relatively simplistic. Something that could operate for thousands of years, with no maintenance but what self-replicating facets had been programmed into it, could not afford to be over-complicated. Downed drone units were torn apart, their robust but direct operating systems repurposed by the caniest Astartes of the 18th, allowing the Legion to now set reprogrammed automata loose upon their fellows, berserker devices shorn of higher functions, and bluntly aimed as unliving weapons. Familiarity with the operating systems of the drones was then pivoted to the vast machinery around the Legion. Access panels provided routes to the core systems of the Tempest Galleries. Ravaging safety and control interfaces with desperate rapidity, the 18th were now able to wield the lightning itself, electromagnetic death to the machines that were besetting them. Massive coronal blasts were threalded as harpoons, driving spears into the cores of larger machines, incinerating hosts of swarming drones. A stalemate was bought, but at horrific cost. 66% estimated casualties, only a third of the original invasion force remaining alive within the Tempest Galleries. The 18th had inflicted significant damage on the machinery around them, but had yet to strike a decisive blow. Even now, the abominable intelligence motivating the technology of the caverns was manufacturing more automata to fight the intruders. Histories of course had no reinforcements at their disposal, forcing their hand and calling for a plan of action to be rapidly formulated. The central power node of the largest cavern chamber thus far discovered, responsible for the transmission of motive force throughout the entire network, was identified as the best target of opportunity. Even if this was not the locus of the entire system, surviving legion commanders reasoned that a massive disruption to the flow of power would at least earn the Astartes further time, and, at best, affect damage to the shields of the ethnarchy fortresses far above, hopefully providing the Imperium with the opportunity needed to begin its assault. The attack would be too prompt, a series of diversionary attacks to draw out the largest attentions of the machines and attract the bulk of their number, while a second and larger division would shortly thereafter assault the power node. It was assumed that this force would simply be annihilated in their efforts, that even should they succeed, death was certain. Legion commanders acquiesced to calls from the rank and file to assign Astartes to this task, not by squad or company, but by lottery. This was not because Battle Brothers did not wish to take part, literally the opposite. All members of the surviving 18th Legion fervently desired to be a part of this, apparently, forlorn last-ditch attack. When the assault came, Legionaries of the 18th would likely have seemed to a casual observer a motley collection indeed. Their Legion as Astartes' standard equipment was either modified or discarded entirely. Instead, they bore improvised power fists and thunder hammers, or cutting saws and lightning cannons torn from the mechanical corpses of their enemies. Multiple strike teams hit simultaneously, falling upon automata with fire and fury, expending all ammunition reserves, withholding nothing in favor of a total overwhelming assault. The intelligence running the galleries responded with all the cold machine logic the Astartes had been counting on, dispatching drone swarms in precisely overwhelming numbers to stamp out each of these strike teams in turn. The forces unleashed on the preliminary diversion attacks possessed a clinical savagery, threatening to annihilate each Astartes squad in turn, but these had succeeded in their role. The second hammer blow struck as soon as it was viable, the assault force supplemented by the 18th surviving dreadnoughts and rapier weapons batteries. Across silicate bridges suspended above churning seas of magma, the Astartes of the Imperium collided with the machine intelligences of a time long since past, the new age of humanity meeting out fury upon its misbegotten creations. The Tempest Gallery intelligence responded immediately, throwing all automata reserves into the conflict, rising the fighting to an intensity unseen in the annals of the Lejeunez Astartes. Bodies by the hundreds plummeted from bridges and ledges consumed by the roiling lava lifeblood of Terra, machine oil and human blood vaporizing in the crushing furnace heat. The advance on the power node was torturous, each meter of scorched rock bought at the toll of a dozen Astartes lives. In logical desperation, the abominable intelligence of the galleries unleashed its final reserve at this critical moment. From within the depths of the magma lakes rose a mechanical cephalopod, a kraken beast set in burnt black diamond, unwinding coils long and powerful enough to crush a titan god engine. The machine set about demolishing the rocky bridges that spanned the chamber, severing Astartes from their longer-range support weaponry, cleaving squads in twain, and consigning hundreds to base incineration in the magma below. All fire simply bounced off its hide, not even the scavenged weaponry could dent the monstrous thing's hull. A fighting retreat was mounted by those few who could, but all who beheld this new engine of destruction knew their chances were futile. There was nowhere to run. The precise nature of what occurred next can only be guessed at. Combs were so garbled and scattered that it itself had no announcement or coordination. Crashing through the cavern walls, preceded by a bow wave of rock and dust, came one of the tunnel-boring spheres, its mouths working even as its sword through the gas and futon-choked air, making directly for the power-node nexus. It is assumed that, based on available evidence, that this machine had been captured by one of the diversionary squads during their engagement, and reprogrammed to serve as a last-ditch reserve attack to supplement the efforts of the main assault force. Others state that one of the intelligence's own machines had, in the cascading chaos of the engagement, simply gone haywire. Programming, overcome by failures of processing efforts. Whatever the actual cause, the impact of the machine on the power-node was catastrophic, the ensuing explosion consuming both in a hammer-blow of kinetic force and energy blowback. The explosion tore outwards, consuming the entire-node cavern. The force and fire funneled down narrow tunnels and into surrounding cave systems. Such was the devastation that, above ground, seismic tremors were detected by Imperial Ospec's grid. Instruction seems to have slaughtered the central server hub of the governing intelligence, for, across the Tempest Galleries, the automata, once so animated in their savagery, simply shut off, never to reactivate. Barely a thousand of the 20,000 Astartes that had been committed to the Tempest Galleries survived the assault. Of their fate, initially Nought was known. Despite the confirmed failure of the shield grid protecting the ethnarchy and the subsequent grand Imperial invasion, nothing was known of what precisely had occurred below the earth. Until, days from the confirmed end of the campaign, a sole termite drill emerged from a dormant volcano near Calstats, carrying the survivors to the surface. Had it not been for the video logs of their helms and hololithic recorders, many in the Imperium would have scoffed at the sheer other worldly horrors they had endured, but their conduct was entered into Imperial record with all possible acclaim. The Emperor himself gathered the legion survivors, presenting them with the laurel of victory for the campaign. This caused some chagrin amongst other Imperial commanders, as the ethnarch, now committed to the Emperor's prison at Kangba Maru, had not been captured by the 18th, nor his eugenicist oligarchs slain by their hands, but the master of mankind once again insisted. In fire and darkness tested became the legion's first motto, and a prophetic one. The Tempest Galleries, their first engagement, set a high bar for the legion's history onward, one that many aspired to live up to, much to their doom and detriment. The Forlorn Last Stand, so redolent of the tales of the galleries, became a pathological obsession amongst the 18th legion in the years of the Great Crusade. Willing to ensure anything for the mission was an impressive trait of any legion, but for the 18th it far too often led them to endure casualties that were essentially avoidable, resigning them to situations that could have simply been avoided. This was all, of course, to be tempered and reforged by the coming of the Primarch Vulcan, but for that I must refer my acolytes to the legion's history record, also accessible amongst this data stack. Until such a time as I may commit to record another Chronicle of the Imperium, Ave Imperator, and Gloria in Excelsis Terra. Otherwise, please like, subscribe, comment, let me know your feedback, and as ever, thank you very much for watching.