The signifiers confirmed the identity of last of the soldiers, and the armoured door slid upwards with a hiss of pneumatics and a gust of cool air that spoke of a vast open space ahead. Beyond the door, the iron-sheathed walls of the prison complex gave way to the rough-cut stone of the mountain’s footings. The smell of cold earth and stone that had once rested beneath the deepest ocean blew from within. Glaringly bright lumen globes provided stark illumination and banished shadows.

Thirty metres in, a pair of servitor-crewed turrets spooled up and snapped towards them, clicking and whirring as target locks were established. Heavy calibre autocannons whined with the rotational speed of their barrels as Uttam stepped into the killing box.

‘Uttam Luna Hesh Udar,’ he said, enunciating each syllable with precise modulation.

The augmetic eyes of the servitors changed from red to green, and Uttam ushered the soldiers through as his rearguard warrior approached.

Sumant Giri Phalguni Tirtha was a veteran Custodian, whose name was said to bear at least seventy-six awarded titles. His armour was polished and carved with words of approbation in addition to his earned honours. Uttam did not know how Tirtha had come to Khangba Marwu. He bore no obvious injury and was in prime physical condition, but rumour said he had once questioned an order from Constantin Valdor.

The master of the Legio Custodes was a stern, uncompromising man, and though Uttam had never had the honour of meeting him, he doubted Valdor was so petty as to banish another from his side for so slight an offence. The Legio valued thinking warriors, doggedly determined men who would question and question again until an answer was forthcoming.

‘Is there a problem, Uttam?’ asked Tirtha. ‘Why do you pause?’

‘No reason,’ said Uttam, ashamed at his lapse into speculation.

‘Then let us be on our way,’ said Tirtha. ‘I dislike being here, the air stinks of them.’

Uttam nodded. The air didtaste different. The unique physiology of the prisoners made them different from mortals, even Custodians, in many obvious ways, but also in many less evident ones. Whatever crimes a man might have committed, he was still recognisably human, still clearly part of the human race. These prisoners smelled subtly different… almost alien, and that rankled almost as much than their betrayal.

Almost.

‘Biometrics confirmed,’ said Uttam, and the security door slid closed behind Tirtha. As the metres-thick locking bars slid home, he said, ‘Primus Block Alpha-One-Zero is now sealed and secure.’

‘So confirmed,’ said Tirtha, striding to the front of the column. Uttam now took up the rearmost position, and took short steps as Tirtha led them down the wide corridor. Though they were selected from the bravest and most professional regiments still based on Terra, there was no disguising the soldiers’ nervousness as they passed between the turrets. Though rigorous safeties had been engaged by Uttam’s command, they guns could open fire in a heartbeat, and the green eye-lenses of the servitors promised no mercy to anyone caught in the killing box.

Uttam followed Tirtha and the soldiers towards a wide archway lined with las-mesh emitters, through which came the bass note of colossal generators and the actinic tang of powerful energy fields. Uttam passed beneath the arch, emerging into an enormous cavern, a kilometre wide at its narrowest part, with glistening walls and a dizzyingly high roof. The cavern had no floor, simply a bottomless pit that spanned its entire width. Uttam knew that such a term was hyperbole of the worst kind, but it was apt for all intents and purposes.

He stood on a wide platform built at the edge of cavern, in the shadow of a slender bridge of latticed steel that reared up like the body of an enormous crane. Tirtha stood at its control console, and Uttam watched as he manoeuvred the bridge towards an island of rock that floated in the centre of the cavern, suspended on a hazy cushion of invisible energy.

Enormous machines like vast engines were bolted around the circumference of the cavern walls and Uttam felt the hairs on the back of his neck stand to attention in the electro-statically charged air. At a moment’s notice, these generators could be disengaged and the island would be allowed to plummet into the depths of the world. With such dangerous prisoners, no chances could be taken.

The bridge made contact with the floating island, and a host of automated gun pods mounted in the walls of the cavern swung long barrels to bear on the island. Thirty isolated cells stood on the floating rock, but only twelve housed inmates.

With the bridge in place, Uttam marched onto the bridge, with the soldiers and Tirtha following behind him. The bridge rang with the sound of his armoured boots, and he kept his gaze focussed firmly ahead of him. He unlimbered his guardian spear from the quick-release sheath on his back and rolled the muscles in his shoulder to loosen them in readiness.

‘Expecting trouble?’ asked Tirtha over the helmet vox.

‘No,’ replied Uttam. ‘But I always feel better facing these bastards with a weapon in my hands.’

‘I know what you mean,’ said Tirtha. ‘I almost hope one of them tries something.’

‘Don’t even joke about it,’ warned Uttam as he reached the end of the bridge.

The first cell was a square block of triple-layered and ceramite-laced permacrete that gave little clue to the nature of the inmate within. Featureless aside from an alphanumeric designation stencilled on its side and a transparent door of armaglas normally found in the viewports of starships, it was a box that no one entered or exited without the say so of the Legio Custodes.

Uttam approached the door, feeling a familiar knot of tension in his gut: the flush of endorphins and battle stims that preceded a combat engagement. The sensation was welcome, even though he did not expect to fight here.

A single figure sat cross-legged in the centre of the cell, his muscular physique barely contained by the bright yellow of his prison-issue bodyglove. Long hair, dark as oil, spilled around a broad face with genetically spread features that should be ugly, but somehow combined in a handsome whole.

Though this prisoner was deadly beyond words, he had a smooth grace that was disarming. Uttam knew better than to underestimate Atharva simply because he came from a Legion of scholars. Where the others raged or spat biliously at their gaolers, Atharva appeared to accept his incarceration without rancour.

Atharva opened his eyes, one a glittering sapphire, the other a pale amber.

‘Uttam Luna Hesh Udar,’ said the warrior. ‘You are interrupting my ascent into the Enumerations.’

‘It is time for you to eat,’ said Uttam, as the nutrition dispenser was slotted home in the clear glass of the door. A cellulose bag of foodstuff dropped into the cell, and Atharva watched it fall with a mixture of distaste and resignation.

‘Another day, another banquet,’ said the Thousand Sons warrior.

‘You are lucky we feed you at all,’ said Uttam. ‘I would let you starve.’

‘Then you would become the villain of the piece,’ said Atharva. ‘And as the Emperor’s praetorians that must never be the case, is that not so?’

‘Do not say his name, you are not fit to speak it, traitor.’

‘Tell me, Uttam, whom had I betrayed when I was brought here?’ said Atharva, uncoiling from his seated position to stand in one smooth movement. ‘When Yasu Nagasena led his three thousand into the Preceptory, who exactlyhad I betrayed? No one, yet here I am locked up in a cell with warriors whose Legions are rightly named oath-breakers.’

‘When a group has a plague-carrier in its midst do you only remove those who are sick or do you quarantine the entire group?’ asked Uttam.

‘Allow me to counter your example,’ said Atharva. ‘If a man develops a tumour, do you selectively destroy it with treatment or do you simply kill the man?’