Seconds later the battle barge replied with a rolling salvo from her bombardment cannons. They boomed through the hull like war drums, each one growing louder as the volley marched closer to the bridge. The shells glowed as they sped through the void and smashed into the flanks of the rebel ship. Nemiel watched in awe as a series of massive explosions rippled through the cruiser's decks, until finally it blew apart in a flare of escaping plasma.

Farther away, the grand cruisers at the centre of the enemy formation were reeling beneath the blows of Imperial torpedoes that struck them both fore and aft. The Forinax staggered out of the formation, her bridge aflame, while the Castigator saw most of her starboard gun decks smashed by a trio of powerful hits. The scout force reduced speed and continued their run behind the rebels, lashing at the enemy ships with their weapon batteries and energy lances.

The Imperial ships plunged through the rebel formation, exchanging thunderous broadsides with the enemy. The smaller cruisers suffered greatly under the punishing blows of Jonson's larger ships; a Crusader received a broadside from both the Amadis and the Iron Duke that ripped her open and left her a burning hulk, while the second Armiger blew apart in another massive fireball as her reactor core was breached. Lances and shells hammered the Imperial ships as well; the flagship and the strike cruisers bore the brunt of the enemy fire, their armoured hulls riddled with multiple impacts and the glowing tracks of lance hits. Duchess Arbellatris staggered beneath a hail of fire; her hastily-repaired hull plating gave way beneath the onslaught, wracking the proud vessel with devastating internal explosions that left her drifting out of control. Flamberge and Lord Dante suffered as well, their upper decks and superstructure smashed by a hail of enemy shells, but the battered heavy cruisers held their course and returned fire with every weapon they had left.

The exchange lasted barely fifteen seconds, though to Nemiel it seemed like an eternity. The void was rent with fire and streams of blazing debris. Ships and men died in the blink of an eye before the two forces drew away from one another on opposite courses. The scout force continued to harry the rebels as they sped away and began a slow turn to re-engage the Imperial battle group.

'Damage report!' Jonson ordered. The Invincible Reason shuddered like a wounded beast as she sped on towards Diamat. The air in the strategium was growing hazy with smoke as fires spread throughout the ship.

Captain Stenius was bent over the Aegis Officer's station, his augmetic lenses glowing green in the reflected light of the flickering readouts. 'All ships report moderate to severe damage,' he replied. 'Duchess Arbellatris is not responding to signals. Flamberge and Lord Dante report heavy casualties. Iron Duke and Amadis have both sustained damage to their thrusters, and Amadis also reports that her flak batteries are out of action. Repairs are underway.'

'What about us?' the primarch said. 'How hard were we hit?'

Stenius grimaced. 'Our armour stopped the worst of it, but we've got hull breaches all over the ship and a fire raging on three decks. The torpedo deck reports that the forward tubes are fouled, but they're working to clear them.' He shrugged. 'It's not good, but it could have been much worse.'

Jonson smiled grimly. 'Don't tempt fate, Captain. We're not finished yet. Signal the main force to alter course to three-three-zero and launch the Stormbirds. We'll head straight for those transports and see if we can force them to weigh anchor. I'm betting the reserve force will opt to disengage rather than risk those ships.'

He turned to Nemiel. 'Brother, it's time you made your way to the drop pods. We'll be over Diamat in another ten minutes.'

There was an ill wind blowing through the halls of Aldurukh, and Zahariel feared he was the only one who felt it.

The courtyard was much the same as it had been when he was a young aspirant; the white paving stones were kept spotlessly clean, the more to highlight the dark grey stone of the spiral that had been laid there many hundreds of years before. The Order had used it as a training tool, incorporating the curving lines into their sword routines and close-order drills, but Brother-Librarian Israfael claimed that its significance was far more ancient. 'Walk the Labyrinth and meditate daily,' he told his students. 'Fix your eyes upon the path, and it will help to focus your mind.'

Zahariel walked the spiral with slow, deliberate steps, his head covered by a deep woolen cowl and his hands tucked into the sleeves of his surplice. His eyes followed the endlessly curving line of dark stone, no longer truly seeing what was before him. The Librarian's mind was turned inward, buffeted by an unseen storm.

He could feel the energies of the warp whipping about him like a gusting breeze, angry and turbulent. Israfael had warned him on the trip back from Sarosh that the winds of the warp were far stronger on Caliban than any other world he'd ever visited, and the senior Librarian had spent considerable time studying the phenomenon since they'd returned. From Zahariel's own observations, it seemed that the energies surrounding the vast fortress had grown increasingly agitated over the past few months. He knew from his training that the warp was sensitive to strong emotions - particularly the darker passions of fear, sadness and hate. Given the troubling events that were occurring beyond the walls of Aldurukh, the rising wind felt like an ill omen of things to come.

The civil unrest spreading across Caliban baffled and troubled Zahariel, all the more so because it had evidently been building for a long time. He was dismayed to discover that the clues had been there all along. After learning of the situation from Luther, he had spent every free moment sifting through the vast message archives in the fortress's library. The Imperium operated and maintained Caliban's fast-growing vox and data networks, and every bit of message traffic - from personal calls to news broadcasts - were captured and archived as standard procedure. So far he'd managed to work his way back through several years' worth of data, and his Astartes training had taught him exactly what to look for. The patterns were obvious to one educated in the myriad ways of waging war.

There was an insurrection spreading across Caliban. It was well-organised, well-equipped and growing bolder with each passing day. It hadn't been going on for months, or even a year, as Luther claimed, but possibly as long as a decade.

Whoever was behind the unrest had been very careful, starting with small disturbances in scattered settlements and slowly expanding as their skill and experience increased. Reports of industrial accidents at weapon manufactories and other industrial sites had been written off in the past as the unfortunate consequence of a highly aggressive expansion program, but now Zahariel wondered how many of these accidents had actually been staged to cover up the theft of weapons and other military-grade equipment. Investigations by Munitorum officials and the local constabulary had been perfunctory at best, but the Imperial bureaucracy on Caliban was overworked and undermanned and there was good reason to believe that the planet's law enforcement organisation had been compromised. There was certainly enough evidence to indicate that the constabulary had been covering up the extent of the problem for a long time, but yet…

How could Luther not have known?

The ghostly pressure of the warp vanished, like a snuffed candle. Zahariel paused, took a deep breath, and tried to regain his focus once more.