An ancient Terran philosopher once created a model of society based around a vast pyramid. He theorised that humanity naturally structured itself into a hierarchy based around a system of duties and obligations. In this great pyramid each level is smaller than the one beneath it, and enjoys more privileges in line with their increased sense of obligation. At the peak stands a single man to whom all others are bound by duty, but so too is he bound by obligation to maintain their holdings. At the base stands the teeming masses, carrying the weight of the world on their shoulders. Though they may suffer, they are the most numerous and their duty is spread over many shoulders. Without them, the whole edifice comes crashing down.

The Hive Cities of the Imperium are this theory put into terrifying reality. The spires taper upwards until ending in the solitary palatial complex of the ruling class. Beneath those colossal heights the hives are like their own, self-contained, society. The vast majority of Hive Castle will never have left the city, and many may not be aware that there is any part of the world that is not formed of steel and rockcrete. They live in a horizonless world of labyrinthine architecture that renders maps largely useless, their days are spent on suspended railways travelling endlessly between kilometres of office space and the towering hab-blocks they call home. Their food is shipped in from across the planet and processed in vast factories to bring out every possible nutrient but even that is not enough and tens of millions rely upon the Administratum grain ration to feed their growing families. The air they breathe has been filtered through the arcane machinery of the Mechanicus to ensure that life-giving oxygen reaches the very heart of the hive.

Hives are built, rather than growing naturally, and so there is a space at the very base of the hive where the gargantuan support pillars meet the abandoned ruins of the city that came before. This Underhive is a warren of twisted architecture bent by time and neglect into a ruin more dangerous than any battlefield. The denizens of this place do not contribute to the hive, they do not factor into census reports or tithe allocations, instead eking out a miserable existence eating algae or mould grown besides pools of stagnant runoff, or preying on the hive’s vermin for meat. These people have no place in the pyramid, but they are too far removed to be considered parasites. They take nothing, instead claiming what little resource flows down from the lands above. Lands that, to them, may as well be another world.

Their world is one of tribal violence and the struggle for survival. It is a land populated by those who fall between the cracks, the destitute, the desperate or those seeking to hide themselves. The most these people see of those above is the occasional figure of a death cultist, unnaturally lithe shadows that bring swift and random death to even the mightiest of warriors. It is a land of mutants, those unfortunate souls whose bodies have been corrupted by the warp into disgusting deviations from the holy human form. Most revel in their horrific state, but a select few are aware of how far they have fallen and many of the Imperium’s most devout subjects are those poor fools who pray in vain for salvation. The truth is that this is no divine curse, nor the result of unfortunate genetics, but rather the by-product of the great power generators mingling with the sheer psychic mass of humanity that dwelt above them.

Amelia could feel this mass as the Valkrie twisted and turned around support pillars and through the ruins of some ancient city. Every human, save blanks, had some form of presence in the warp and when humanity is concentrated into one place their minds can resonate off each other to create a sort of gestalt field. The lower down in the spire, the greater mass of psychic energy lies above you and the greater the risk of that mass corrupting the human form. This far down Amelia felt like she was working underwater, the air was sluggish with psychic energy that pooled in a great mass, neither chaotic nor divine. Further up, this miasma amplified people’s emotions, inflaming mass hysteria or people’s inherent violent tendencies, but in these depths its crushing weight instead created an air of futility, only amplified by the decrepit surroundings. The only people who lived down here were the forgotten, the destitute or the desperate, and only one of those categories merited the attention of the Inquisiton.

Michelangelo Borgia was not born to nobility, but he harboured ambition that outstripped the circumstances of his birth and had dedicated his life to the acquisition of power. He had begun in the streets of the Lower Hive, where he had bullied his local gangs into submission until he controlled the narcotics trade in and out of his small duchy in the lower city. The Ragged Duke, the people took to calling him, and he leaned into his new identity with eager ambition. From this small foothold his empire spread out of the hive and into the countless refineries and warehouses that filled the miles of naval and orbital dockyards that ringed the hive, using the rudimentary workers unions to seize control of factories in a shadowy war that went largely unseen by the wider hive. He kept his men’s allegiance secret until, in a single night, the entire docks district was shut down by strike action and the Governor’s enforcers were overwhelmed by armed mobsters. His tactics succeeded in earning him a slice of the vast revenue that flows through the docks, filtered through shell companies and deputies, but it also made him public enemy number one.

The PDF were deployed to his Duchy and the Ragged Duke was deposed as a sixteenth of the hive descended into blood and fire. He fled from the public eye into the Underhive, where he found his home amongst the mutant clans, who he supplied with arms and armour in exchange for their loyalty. The docks still belonged to him, though that could never be proven, but he would never again be the grand Duke who toured his kingdom on a chariot, surrounded by the cheering of his supporters. Since then, he had waged a secret war against the Nobility and their Death Cults, sending teams of mutant killers up into the hive to bomb Constabulary precincts, raid noble houses, assassinate his enemies and fight the Death Cults on their own ground. The Inquisition believed that this loss of power had wounded him, and that he would relish a chance to return to the public eye. They also believed that his relationship with the Mutants was one of convenience, and that he would cut his ties for a chance at the power he so obviously craved. They also knew him to be a competent administrator and strategist, and so Amelia had been dispatched to the depths of Hive Castle to find him and make an offer he can’t refuse.

‘These tunnels are getting too narrow for us Ma’am, I’m afraid you’ll have to proceed on foot’

The crackly voice of the pilot emerged through the intercom, breaking Amelia away from the psychic miasma and bringing her firmly back into the here and now.

‘Understood, set us down as far in as you can, then withdraw. We’ll signal you when we need a pickup.’

‘Roger, setting you down now. We’re around four miles away from the settlement, providing our maps are accurate.’

‘Alright everybody, respirators on.’

The order war largely redundant. Amelia shared the Valkyrie with a squad of ten stormtroopers, led by Corporal Al’Said, and they all wore respirators built into the helmets of their carapace armour. Indeed, Amelia had never seen any stormtrooper outside of his helmet while on shift, even her own men had only removed theirs once they were off duty. The final passenger was her Adjutant, Helena Brazier, and here the order was a necessity. The girl still wore her ubiquitous grey robes, which Amelia doubted would hold up to the difficult terrain of the Underhive, and her bulky respirator served to hide the naked terror that sat plainly on her face. She had grown up in a hive, and viewed the Underhive in much the same way the Imperium viewed the Eye of Terror.

Amelia clasped the buckles on her own rebreather, a mask that covered her face but left the rear of her head free, so as not to interfere with the cabling of her psychic hood. Breathing through the mask was difficult, there was a strange feeling of resistance as her breaths drew against the filters, but it would see her through the Underhive safely. The only air that came this far down was the scant breeze that drifted in from outside, or recycled air from the hive above, and though much of it was safe for a human to breathe there were pockets of deadly gas in the depths, and the air carried a horrific cocktail of diseases.

This fetid air rushed in as the Valkyrie set down, rushing into the opening doors to match the aircrafts lower pressure. Hazy light from the Valkyrie’s running lamps illuminated their surroundings. They had set down atop the roof of an ancient hab-block that, by the ravages of time, now lay level with the surrounding ground. Vast beams of hardened steel and ferrocrete rose out of the surface at regular intervals surrounded by great hills of sediment that stretched upwards in a man-made amalgam of stalagmites to meet their counterparts descending from the ceiling. The whole cavern was barely lit by running lights that stretched along the base of the hive, placed not for the benefit of the underhivers but rather the use of the Public Works Department who would on occasion descend into these depths in armed bands a hundred men strong to verify the integrity of the hive.

Before Amelia rose a veritable mountain of twisted metal, the remains of some ancient hivequake, where a section of the Lower Hive had collapsed. The vast edifice was honeycombed by twisting tunnels where roads and corridors had been partially buried. The mass blocked their gunship from the largest known settlement and Amelia waved the pilot off. Scraps of muck and dust were scattered as the aircraft rose before turning on its axis and flying off into the hive, back towards the glorious light of day.

Its departure left the team in the half-light of twilight and the light filters in the lenses of their respirators activated, enhancing the low light and giving their eyes an eerie green glow. It was in this strange twilight that Amelia checked her map. The government had collected survey data this far down, but the most recent information was a century out of date. The map she carried on a small datapad had been compiled based on paper maps captured off the Death Cults as well as the intelligence of the only one of the Inquisitor’s covert operatives to have been operating in the underhive. The information was still largely speculative, but it did record the location of Waterfall, the settlement where she was to meet this undercover operative, and her current location, meaning all she had to do was find a route between the two points.

A quick study of the imposing ruin before her identified a motorway that had fallen on its side, resulting a tall tunnel with only minor structural damage. With crampons, spikes and lengths of rope they were able to clamber up the slopes of rubble and into the motorway wreckage. Her stormtroopers took to the task with stoic professionalism but Helena suffered a great deal on the ascent. Her robe, as Amelia had guessed, was repeatedly caught on spars of metal and the base began to resemble frayed rags. This stretch of motorway had survived because it had been built into the side of a long stretch of hab-blocks and so Amelia strode along the side of a vast building, occasionally stepping over panes of shattered glass or around the wreckage of vehicles. To her right rose the four-lane motorway, its surface cracked from the great weight that now rested upon it as much as from the collapse itself. The tunnel was pitch black, save for the beams of light that emanated from underslung or handheld torches, and great shadows stretched out from twisted wreckage. Occasionally a beam of light would pass into the open windows beneath their feet and Helena would shudder at the unburied bodies that lay within, killed by the fall or starved in the aftermath and little more than skeletons now.

Five miles in the highway they had been following ended in a twisted wall of steel and concrete that completely blocked their path. Auspex scanners were brought out to scan the surrounding walls. The handheld devices were normally used to identify moving targets from behind walls, but here they were better suited to identifying empty space, to find a usable route through. The most satisfactory option lay beneath their feet and the remaining panes of glass were smashed away from a broken window. The team helped each other through the gap and down the eight-foot drop from wall to wall. The team proceeded quickly through the one room hab into the corridor beyond, each taking care not to dwell on the crib of painted plastic that lay crushed against the oven. The corridor beyond was not meant to be travelled sideways and they crawled in the meter and a half of space that separated the two walls. Eventually, they came across an elevator shaft that had been built into the support pillar of the building itself, and as such was largely intact. It lay laterally along the wall of rubble, and as such would bring them no closer to their destination, but by traversing its length Amelia was able to sound out another passage that would bring them the right way.

Amelia first felt their presence as she led her men through the twisted remains of a commercial block where the better off residents of the Lower Hive had gone to purchase the simple luxuries of the common masses of the Imperium: clothes, toys or sturdy footwear. As they clambered across the wreckage, she began to feel the presence of other minds in the distance, and of a single figure watching them from a great distance. Seemingly satisfied by what it saw, this mind moved stealthily back to its fellows, who began to slowly creep into the surrounding shops some hundred metres ahead.

Amelia spoke, and her voice was carried through microbeads to the rest of her team.

‘There are twenty-four locals planning to ambush us as we pass the grocers, an equal number on the left and right as well as two in the ceiling.’

‘Roger’ came Corporal Al’Said’s reply in a detached, professional, tone ‘Act like we haven’t noticed them. Charlie fire team take the right, delta take the left. Ma’am, can you deal with the two in the ceiling?’

‘Certainly.’ Amelia spoke with unfeigned confidence.

They moved forward seemingly unaware of their ambushers, even Helena managed to contain the fear that ran rampant through her mind. The very moment the enemy seemed ready to attack, Corporal Al’Said gave a single word of command and twin grenades were sent flying to the left and right. They burst mid-air in a flash of light and sound that effectively blinded their ambushes whilst the sophisticated light filters of the Inquisition detected and compensated for the sudden change. In an instant the stormtroopers dropped to one knee and began firing into the shops, catching the two or three figures appointed as lookouts before the second, live, grenades detonated and they leapt to their feet, storming the building with utter ruthlessness and mowing down the mutants within.

Mutants they were, Amelia came to realise. Each ragged figure sported some disgusting oddity, from a man whose bare torso exposed scales rather than skin to a five-eyed woman who stood on two stumps of bone below her knees. With a single blast from her laspistol she gutted the first of her two targets. Her enemy had been preparing an improvised grenade to toss down and the repurposed tin can detonated in his twisted arms, sending much of the ceiling crashing down and depositing Amelia’s watcher onto the ground before her. The mutant child could not have been older than twelve, though it was hard to tell, and short spines of bone jutted out of her at irregular intervals. She made to stab Amelia with a dirk of salvaged steel, but the barrel of a laspistol in her face and a blast of psychic energy convinced her to stay on the ground.

The sound of a gurgling scream being cut short by a lasbolt informed Amelia that the Stormtroopers had done their job, and the armoured figures soon began to scramble back over the rubble. The mutant child, surrounded by masked figures with green glowing eyes, was evidently terrified and prostrated herself at Amelia’s feet, begging for mercy in a bastardised low gothic. Amelia built a subtle psychic aura around her men to make them even more terrifying and, as the girl cringed back in fear, she leant closer to the child’s face.

‘What is your name, girl?’ Her voice was distorted by the mask into an unsettling rasp.

‘Luka, master. Luka begs your mercy. Luka didn’t know your strength.’

The child had taken to clutching her knees to her chest, and Amelia could see her spines drawing blood as they met her skin.

‘Does Luka know the way to Waterfall?’

‘Yes master, Luka’s tribe went there often to trade treasures from the wall, or slaves captured in it…’

Those last words were spoken in a hushed whisper, and Amelia could feel the conflict in the child’s mind. She didn’t want to tell the warriors her tribe meant to sell them as slaves but she was too afraid of them to omit anything.

‘You will take us there.’ This was not a question, but Luka still felt the need to respond.

‘Yes, kind master! Luka’s life is yours!’

The poor child was true to her word and led them through the twisting tunnels of the hive with the practiced air of a native in this strange land. At times Amelia would feel Luka’s shock at how the Inquisitor’s party staggered their way through the tunnels, reserving a sort of disdain for Helena’s amateurish efforts, but she was far too afraid of her captors to make any comment. She brought them away from the commerce centre and into what must have been her home; a few dozen old mattresses surrounding a fire built into an old rail station. Trinkets and tribal fetishes decorated the walls and Amelia could feel tears form on Luka’s face as she was reminded of her bereavement. She wiped the tears away with a scrap of clothing, determined to prove her strength to her new masters so they wouldn’t kill her too. From here the path was better trodden, and the fire team was able to move through the rest of the wreckage at a brisk walk. It had been the better part of nine hours since they first finished the climb to the motorway and the sudden sight of open space struck them all dumb.

The ‘Wall’, as Luka called the collapsed section of hive, looked over a vast cavern that could have almost been agrarian. The landscape was all twisted metal and heaps of refuse but much of it was covered in a green moss that glowed ever so faintly. Water pooled in the shattered remains of old buildings or flowed down streets and natural channels in small rivers and streams. The flow originated from a cascading waterfall that fell from an enormous pipe that stretched across the diameter of the cavern some twenty kilometres long. This was the old river whose banks the city of Castle had originally been founded on, caged by the Mechanicus in this vast pipe to keep the hive supplied with water, and to keep the ground firm beneath their feet. The town of Waterfall squatted around a great lake into which a torrent of water cascaded down from a leaky joint. Somewhere amongst those ramshackle hovels of repurposed metal was her contact, the first step in finding the Ragged Duke amongst this man-made hell.