We followed the silver path. It passed through a tetragate, and at once we found ourselves in another garden chamber, similarly filled with glossy, abundant plant life thriving in sculptural tanks. The tallest growths in here - giant yellowish horsetails streaked with orange veins - rose eighty or ninety metres above the floating pathway.

  Guilar called a word of alarm, and his storm bolter began to fire, raking across this second chamber from the silver path on which we walked. The shots burst gourd-like plants in fibrous bursts of sap and hacked shreds of leaf and tendril into the air.

  Return fire came at us. Las-fire and the crack of autorifles. Through the sickly growths of this indoor jungle, the soldiers of the heretics moved against us.

  TWENTY-FOUR

  Purge Two engages.

  A silent revolution.

  Dazzo's triumph.

  They came through the plant growth, along the silver paths, blasting, men clad in the stained uniforms of the 50th Gudranite Rifles and the black armour of the naval security detail. Two of the Gudrunites in my squad toppled and fell from the path, their corpses disappearing into the oily waters of the tanks below. But most of the enemy gunfire was going wild.

  Purge Two countered, lasguns barking. I moved to the front of the group and began firing my bolt pistol. There was precious little room for manoeuvre on the silver walkway, and even less cover.

  My first shot went wide, so wide I wondered if the bolter was misaligned. Then I remembered the devious nature of the sarathi tetrascape and compensated. Two shots, two satisfying hits. Bequin and Midas both had the trick of it too, and Jeruss's boys were learning.

  Guilar made a lot of noise, ripping through the gardens with his storm bolter. But it seemed to me he was still discomforted by the environment.

  It was a salutary moment. To see one of the god-like warriors I have regarded with great awe ever since the day, thirty years ago, when I watched the White Scars take Almanadae, become fallible. For all his power, courage, superhuman vigour and advanced weapons, he was achieving nothing, whereas Yeltun, the youngest of the Gudrun boys, had made three kills already.

  Was it arrogance? Overconfidence in his own abilities?

  'Guilar! Brother Guilar! Adjust your fire!'

  I heard him curse something about insolence, and move ahead down the path, detonating plant bulks with his shots.

  'Why doesn't die bastard listen?' Midas complained, sighting his Gla-vian rifle and decapitating a heretic trooper at one hundred metres.

  'Close up!' I ordered. 'Jeruss! Frag them!'

  Jeruss and three others began to lob frag grenades over the thickets. Explosive flashes blew water ooze and vegetable matter up from the tanks, and the air became foggy with plant fibre and sappy moisture.

  There was an abrupt change in tone in the enemy fire. The boom of a bolter rang out over the crack and snipe of the laser weapons.

  I looked down the silver path in time to see Guilar jerk backwards as multiple bolter rounds struck his chest plate. With a cry of rage rather than pain, he went over, off the path, into the bubbling water of the tank behind us and vanished.

  Thrusting the heretic foot soldiers out of the way, his killer came down the pathway towards us.

  'Oh no!' Bequin cried. 'Please-by-the-Golden-Throne-no!'

  Another of the Emperor's Children, the brother if not the twin of foul Mandragore. His scintillating cloak blew out behind him, and his steel-shod hooves shook the path. He was bellowing like a bull auroch. His bolter spat and the Gudrunite beside me burst apart.

  The Children of the Emperor, shadowy sponsors of this entire enterprise, were here to protect their investment. Had they come, unbidden, after Mandragore's death? Had Dazzo or Locke summoned them?

  I fired the bolter at him, joining the fusillade of desperate weapons blasts that Purge Two levelled in a frantic attempt to slow him down. Fear made the men forget the best of their training, and many of the shots were wild. He didn't seem to feel those few that struck his armour.

  'Purge Two! This is Purge Two! The Children of the Emperor are here!' I yelled into my vox. I knew I would be dead in an instant. It was imperative that Fleet Command knew of this dire development.

  A black shape burst up from the dark water, cascading froth and ooze in all directions. Brother Guilar slammed into the Chaos Marine, wrenching him over, and they both fell thrashing into the adjacent tank. Something, probably the heretic's bolter, fired repeatedly underwater and the side of the tank below the floating path splintered out in a rash of liquid. The soupy water flooded out, draining away into the gullies between the garden structures. As the fluid level dropped, the titanic combatants emerged, blackened with mire, wrestling and trading inhuman blows among the tangled roots and feeder tubes of the tank's murky bottom.

  Ceramite-cased fists pounded into armour plates. Chips of plasteel flew from the impacts. The Chaos Marine's vast paws clawed at Guilar, tearing at his visor and shoulder guards. Guilar drove him backwards, his feet churning in the shallow, thick water. They slammed in the bole of a cycad. The enemy grappled, getting a better grip, stabbing a jagged gauntlet spike

  through the armpit seal of the Deathwatch's imperator armour. Guilar staggered, and as he fell back, a massive backhanded slap knocked him over and tore his helmet off.

  The Chaos Marine landed on the sprawling Guilar, tearing at his throat, driving fists like boulders into his face.

  There was a bang of weapon discharge and a flash. His face destroyed and his collapsed skull burning from the inside, the Chaos filth fell back into the swamp water.

  Guilar rose, unsteady, his storm bolter in his hand, blood pouring from the wounds in his face and neck.

  It was a formidable victory. Jeruss and his men cheered and whooped and then renewed their advance on the remaining heretics. The enemy, resolve lost, pulled back and vanished into the dense thickets of the gardens.

  Dripping, Guilar climbed back onto the path and looked down at me.

  Tm glad you're still with us, Brother Guilar,' I said.

  We traced the paths on through the gardens of the saruthi, unopposed. The enemy dead we passed - floating in the tanks or sprawled on the pathways - had signs of branding on their faces. Chaos marks, burned into the skin by evil rather than heat. Admiral Spatian had hoped that some of the heretic forces, especially the Gudrunite Imperial Guard, might yet be restored to the Imperial cause. Like feruss and his men, most had been unwilling pawns caught up in Estrum's treason, and the fleet tacticians had presented models of victory wherein Locke and Dazzo found the bulk of their ground forces turning against them.

  Such a hope was dashed. The minds of these good men had been burned away and poisoned by Chaos. The heretics had enforced the loyalty of their stolen armies.

  Via tetragates we advanced, passing through six more garden spheres, then on into wide, tiled courtyards and halls of asymmetrical pillars whose function we could not imagine. Twice, we had brief skirmishes with heretic forces, driving them back into the warped cavities of the edifice. More often, we could hear ferocious war, full-blown battles that seemed right at hand but of which there was no visual or physical trace.

  Contact wim fleet command was fragmentary. Purge One - Lord Rorken's party - was locked in combat somewhere, and nothing had been heard of Molitor's Purge Four. Schongard's group, Purge Five, was lost somewhere in the tetrascape. Plaintive calls for aid came from them at irregular intervals, piteous half-sane ramblings about 'impossible spaces' and 'spirals of madness'.

  From Titus Endor we heard nothing.

  The main surface war still raged. Mirepoix commanders reported gains along the fire lakes that edged the target edifices, one of which was reportedly beginning to implode as if great harm had been done to it internally.

  In a vault of smooth, polished beige that seemed to us to have no ceiling, we found our first saruthi. They were dead, a dozen of them, their grey bulks split and mauled, silver stilts torn off. Through the next gate lay a spiral room littered
with a hundred more. Moving among the grey dead, their pallid limbs dripping with ichor, were several of the white slave beasts that had carried the Necroteuch onto the plateau. They seemed to me to have broken free as many dragged their wire restraints. Some had taken up silver stilts and were stabbing them slowly and repeatedly into the corpses of their grey masters.

  I wondered if the pitiful white things were a separate race enslaved by the saruthi, or a bastardised, mutant caste kept in servitude. The invasion, it seemed, had freed them to turn on their owners and butcher them. Such is the price of slavery, sooner or later.

  The slave-things offered us no threat. They didn't even appear to notice the humans moving amongst them. With silent, methodical determination, they mutilated the bodies of the saruthi.

  In another chamber, an oval dish with tessellated tiles and a strangely warm atmosphere, living saruthi milled aimlessly in their hundreds. Some had lost stilts and were limping, others lay in trembling masses, their skulls flopped back on their bodies. The smell of liquorice, or whatever it was, reeked here. As we watched, white slave-things lumbered into the chamber through another tetragate and began to twist apart and maul the saruthi, one by one, with the calm, methodical motions of insects. The saruthi offered no resistance.

  This story was repeated in other chambers and curving halls, saruthi lay dead or meandering without purpose, freed slaves finding them by touch and dismembering them.

  I wonder, even now, as to the meaning of these alien scenes. Had the saruthi given up, resigned to their doom, or had some other circumstance stolen their will to live and resist? Not even the tech-priests or the xenobi-ologists could provide an answer. There is, ultimately, only the fact of their alien nature; abstract, inscrutable and beyond the capacity of the human mind to fathom.

  When we found the archpriest Dazzo, he was close to death.

  A battle of titanic proportions had taken place in the tetrascape where he lay. Thousands of dead lay on the tiled floor: Mirepoix infantry and heretic troops alike. Two Children of the Emperor and three Deathwatch were among the fallen. The tetrascape, by far the largest of any we had seen in the edifice, reached away beyond the curve of all human dimensions, and the jumbled corpses covered the endless floor into infinity.

  Dazzo lay at the foot of an asymmetrical block that rose from the tiles like a standing stone. His body was torn by gunshot wounds. Heldane sat nearby, his back to the great block, guarding the archpriest with an autopis-tol. Heldane's torso was smirched in blood and his breathing was laboured.

  He saw us approach through the tetragate and lowered the gun weakly.

  'What happened here, Heldane?'

  A battle/ he said, wheezing. 4Ve came upon it as it was raging. When Inquisitor Endor saw this wretch, he drove us into the fight to reach him. It was a blur after that.'

  Where's Endor?' I asked, looking around, hoping I would not see his corpse among the dead.

  'Gone... gone after Locke.'

  'Which way?'

  He pointed weakly to a tetragate on the far side of the sea of bodies.

  'Does Locke have the Necroteuch? The saruthi Necroteuch, I mean?'

  'No/ Heldane said. 'But he has the primer/

  The what?'

  'Dazzo got it out of this thing somehow/ he said, slapping the stone block that supported him. A language primer. A translation tool. Without it, the saruthi version of the text is unreadable to us/

  'How in the Emperor's name did he do that?' Guilar asked.

  'With his mind/ Heldane said. 'Can't you feel that after-burn of the psychic effort?'

  I found that I could. The mental taste of a mind almost burned out. The raised block was clearly another part of the saruthi's mysterious technology, perhaps the equivalent of an Imperial cogitator, perhaps something more sentient, even something alive. Dazzo, whose psychic abilities I already knew to be monstrous, had identified it and psychically assaulted it, forcing it to give up its secrets. An extraordinary feat of the mind, a triumph of will.

  A polyhedron/ Heldane added. 'Irregular, small, made of pearl, it seemed to me. It just came out of the block into his hands. Materialised. I saw it happening as I fought my way to them. But the effort destroyed his mind. Endor cut him down. He hadn't the strength to resist/

  'How do you know it was this... primer?' asked Bequin.

  'I read it in his dying mind. Like I said, there is no resistance left there. See for yourself/

  I crossed over to Dazzo and knelt next to him. Ragged breathing sucked in and out of his bloody mouth. I drove my mind into his, pushing aside pathetic strands of denial, and confirmed Heldane's story. With inhuman willpower, Dazzo had wrenched the language primer from the saruthi technology, and with it the whereabouts of the xenos Necroteuch. Dying, he had passed both to Locke to finish the task.

  'Gregor!' Midas hissed. I turned. Far away, across the curve of the tetrascape, heretic troops were advancing through the dead. They began firing at us.

  Guilar and the Gudrunites fired back, taking what cover they could to resist.

  'Brother Guilar, I need you to hold these bastards at bay/

  Where are you going, inquisitor?' he asked, sliding a fresh clip into his storm bolter.

  After Locke and Endor, to do what I can/

  TWENTY-FIVE

  Xenos Necroteuch.

  Endgame. The blank-eyed man.

  We left the firefight behind us and plunged through the tetragate. Bequin, Midas and I, racing as fast as we could through the disorienting spirals and imbricating segments of the dying saruthi edifice.

  As we ran, I reported the situation to fleet command, but had no reply or way of knowing if they'd understood me. Then I tried Titus Endor, but the vox was dead.

  Moving at speed, the place became even more of a four-dimensional maze, but I had in my mind now the engram I had taken from Dazzo, the memory trace of the route to the xenos Necroteuch he had ripped from the block.

  By my estimation - and it could hardly be trusted - we were approaching the heart of the edifice. Perhaps not the physical or geographic heart, but that part of the dimensional construct buried most deeply in the interlocking lamina of warped space and time.

  There were more saruthi here, skittering and clicking around on their silver limb-braces without purpose or response. The smell of liquorice filled the warm, glowing tunnels and tiled chambers.

  We heard screaming ahead of us, and the thump of gunfire.

  Titus? Titus! It's Eisenhorn! Do you read?'

  The vox coughed into life. 'Gregor! For the love of the Emperor! I need-'

  It broke again. More shots.

  We hurried through a tetragate and almost at once had to dive for cover as las-fire flurried around us. The chamber we had entered was by no means the largest we had found in the place, but it was singular. Dark, and gloomy, it lacked the radiance that shone from the walls and floors elsewhere. The lustrous material that composed the rest of the edifice was here grey and dissected, as if dead.

  Another block, like the one Heldane had been propped up against but many times the size, rose from the ashy floor, streaked with oily, greenish matter that ran down its flanks and pooled at the base. An asymmetrical shelf jutted from it, just above the height of an average human, and a blue octahedron sat upon it, glowing internally.

  The xenos Necroteuch. Dazzo's engram immediately confirmed it.

  The chamber stank with its evil, the liquorice smell, so rich and cloying it made us gag. Behind and above the main pillar, warped sculptures of metal, bone and other organic materials grew from the walls and curving roof. Vicious hooks on filthy chains dangled from these outgrowths. This was not saruthi handiwork but a touch of pure Chaos, spawned by the Necroteuch, infecting the xenos fabric of its sanctum.

  Smaller pillars, irregular and unmatched, dotted the floor around the main block. In between them, a gunfight was raging. The three of us ran from the exposure of the lit tetragate and found shelter behind the nearest of the smaller blocks. Las-s
hots wove in and out of the stone shapes, ricocheting and rebounding.

  Titus!'

  'Gregor!' He was twenty metres away, a third of the way into the chamber, huddled behind a block and firing his laspistol at figures closer to the Necroteuch's resting place.

  I glimpsed Locke, and eight or nine heretic troopers.

  I looked to either side of me at Bequin and Midas. 'Choose your targets/ I told them. We began to fire in support of Endor, dropping at least one of the heretics. As they reeled from the salvo, Endor leapt up and ran forward. A las-shot clipped him and blew him back against a stone upright.

  I ran forward myself, firing my bolt pistol which I had braced in both hands. I blew chunks from the blocks ahead of me, and hit at least one of the enemy gunners. I reached Endor.

  He was wounded in the chest. It would be fatal if we couldn't get him clear quickly. I pulled him into cover, and waited while Bequin ran up through the rows to my side.

  'Pressure, here!' I said, showing her, my hands wet with my old friend's blood. She did as she was told.

  I became aware of thunderous noises from beyond the chamber. The place shook. More thunder rolled and a section of the curved ceiling suddenly splintered and collapsed, cascading wreckage down, allowing cold exterior light to shaft in. A second later, three more holes ruptured and burst through the roof, and from outside I could hear the muffled hammering of bombardment.

  'Midas!'

  He was already moving up to my left, ditching his needle rifle for the pistols in the tight confines. Lethal Glavian needles hissed through the air. The ground continued to shake. A further section of roof came down.

  Leaving Endor with Bequin, I ducked from pillar to pillar, braving the deluge of shots. Midas and I switched to our earpiece links and Glossia.

  'Thorn ushers Aegis, a tempest sinister/

  Aegis attending, tempest in three.'

  I counted the three beats and ran forward as Midas hurled his frag grenade to my left before opening fire with both pistols.