The detonation of the energy conduits triggered a violent chain reaction.
Under the frantic direction of the Tech-Priests, the geothermal extraction systems of the Massif Ballistus, which plunged directly into the planetary core, were abruptly shuttered. This failsafe simultaneously crippled the power grids across the surrounding sectors. Even from the void of space, vast swathes of darkness could be observed swallowing the great cannon and its colossal sub-structures. Deprived of its lifeblood, the miracle of engineering fell silent and paralyzed.
Lurking beneath the veil of cloaking fields, T'au reconnaissance vessels immediately detected the anomaly. Soon, a drone ship, hastily refitted by Earth Caste engineers, drifted cautiously toward the cannon's defensive perimeter. The titan remained dormant; it did not vomit its world-shattering munitions as it usually did.
Though the fate of her infiltration teams remained unknown, Commander Shadowsun recognized this as the definitive moment to uproot the planet's defiance.
The T'au fleet struck with the suddenness of a lightning orrery. A massive force, comprised of twelve Custodian-class Battleships, six Explorer-class Battleships, three Kroot Warspheres, and swarms of Hero-class and Merchant-class cruisers, bore down upon the Kessandras System, which was held by the battered remnants of Indomitus Crusade Fleet Quartus and local Sector naval elements. Orca-class gunships and Defender-class starships hovered in the wake of the capital ships, saturating the void with a relentless storm of railgun fire directed at the Imperial line. These hundreds of vessels represented nearly half of the total strength assigned to the T'au Sixth Sphere Expansion. They moved with overwhelming momentum to crush the Imperial defenders.
On the planet's surface, the Imperial Commander turned to the senior Tech-Priest with a gaze of flint.
"Is the Massif Ballistus still operational? Can it be forcibly engaged?"
Had the cannon remained active, a single shell could have vaporized a quarter of the xenos fleet. Two salvos would have ended the T'au threat entirely.
The Magos's reply, however, was laced with clinical despair.
"By the Omnissiah's grace, my calculations indicate that a forced ignition carries a probability of energy rupture exceeding 85%. The likelihood of a successful firing sequence is below 3%. Conversely, the probability of total power-conduit collapse is 97.2%, and the chance of such an event shattering the tectonic integrity of Volkus itself is effectively 100%."
The commander, a veteran of the doomed Fourth Fleet, displayed a chilling resolve. He turned to his adjutants.
"Signal all orbital assets to engage the enemy."
Then, he looked back at the Tech-Priest.
"If the Navy fails to repel them, you will initiate the forced ignition of the Massif Ballistus immediately. Even if we must grind this world to stardust, neither this planet nor this miracle of the Machine God shall fall into the hands of the xenos!"
The Tech-Priest's face, a ruin of bionic optics and sub-sensory arrays, flickered with a mix of mechanical hesitation and organic dread. He was clearly loath to execute a directive that amounted to planetary suicide. Trembling, he raised a mechadendrite and stammered.
"But... honored lord, pray allow me to present the logic of the Machine God. I have processed every permutation of our current tactical standing. If we commit the Navy to an interception, our probability of total victory is a mere 31%. Should we choose to fortify the surface and hold until the arrival of the next reinforcement wave, the success rate rises to 43%."
The Tech-Priest's binharic cant increased in tempo as his metallic limbs gestured emphatically.
"If we utilize the entire naval fleet in a war of attrition to buy time, the probability of holding until reinforcements arrive increases to a respectable 55%. Therefore, I strongly advise deploying all orbital assets as a screen before withdrawing to the surface to meet the enemy, thereby preserving our strength for the relief force."
The Commander remained unmoved by the Magos's logic. Fleet Quartus was already a broken thing. Should he survive this day, he felt he could not face the Lord Regent or the Emperor with his honor intact. If he were to die in glory, perhaps his soul might yet find its way to the Golden Throne.
His face was as cold as frost, his eyes piercing the Tech-Priest as he barked an ultimatum.
"Enough! If you do not wish to be summarily executed by the Inquisition, move! Do not think I am blind to the calculations of your cogitator-brain. I am certain even your Machine God would not dare stay my hand in executing a coward!"
The Magos's mechanical hands twitched, gears and pistons emitting a low, rhythmic click-clack that betrayed his internal struggle.
"Commander, I shall obey. Yet I must remind you once more: the destruction of a world is a grievous loss to the Imperium. To force the Massif Ballistus is to operate far beyond the sacred safety thresholds. Should it fail, it is not merely death, it is a profanation of the Machine God and an abyss for us all."
The Commander's gaze remained iron.
"This is a strategic necessity. For the victory of the Imperium, we must walk this path. You will await my signal, Magos. I will provide you an escort to ensure nothing interferes with your duty at the critical hour."
With a sharp gesture, a squad of Tempestus Scions marched forward, falling in behind the Tech-Priest. They were tasked with escorting him to the deepest control sanctums of the Massif Ballistus. They would ensure the Priest's survival, and they would ensure the Commander's final order was carried out to the letter.
…
In orbit, the Imperial Navy fleet had struck a defiant battle formation, spearheaded by three Retribution-class and three Emperor-class Battleships. These gargantuan vessels were the primary survivors of the Fourth Fleet.
Exploiting the superior range of Imperial macro-cannons over T'au rail-tech, the fleet unleashed the opening salvo. Twelve massive macro-cannons on the broadsides of the Retribution-class ships spoke first, gouts of fire erupting into the void. Wave after wave of prow-mounted torpedoes surged from their tubes, banking through the silence toward the T'au vanguard. Lance batteries along the dorsal ridges began lashing out, seeking the lighter T'au escorts.
Simultaneously, the Emperor-class battleships threw wide their cavernous hangar bays. Each launched eight full wings of strike craft, half comprised of Fury Interceptors to screen the advance, the other half Starhawk Bombers. These bombers dove into the wake of the torpedo salvos, intending to weave through the enemy screen and deliver their payloads directly into the heart of the xenos fleet.
In the shadow of the capital ships, Firestorm-class Frigates and Scimitar-class Escorts sheltered behind the flickering void shields of Lunar-class Cruisers and Armageddon-class Battlecruisers, adding their own frantic fire to the storm.