Before his engine's horrifying destruction, Suzak had fought like the killer he was, dispatching a Reaver and a Warlord before the Imperator had slain him. On the right flank, Princeps Sharaq and Metallus Cebrenia had, together with Princeps Kasim and Raptoria, taken down the last Reaver, which left only the Imperator, Aquila Ignis.
The Mortis engines had come expecting an easy victory, and no matter what happened next they would leave the bulk of their force burning on the Martian sands. Tempestus had earned themselves a legendary place in the history of Mars.
'It's firing!' shouted Kuyper.
Cavalerio opened a Manifold link to his surviving warriors. 'All Tempestus engines, this is the Stormlord—'
Princeps Cavalerio never got a chance to finish his order as a thunderous series of impacts smashed into his engine. Searing pain, worse than the death of his beloved Victorix Magna, surged through his body as the weakened shields collapsed under the barrage of missiles from the Imperator's upper bastions.
Deus Tempestus's shield emitters blew out in a cascading series of explosions, and the Stormlord's body spasmed in its tank as the feedback blitzed through his mind, fusing his synapses with those of the Manifold.
In his last seconds of life, he saw the heroic march of Metallus Cebrenia and Raptoria as they advanced upon the red and silver monster. Their weapons arms were wreathed in fire as they advanced, heedless of the impossibility of ever hurting the Imperator, though to call it such now that its masters had turned to the cause of treachery seemed perverse.
Metallus Cebrenia was the first to die, her right leg blown off, and an almost scornful barrage of rockets finishing her off as she lay helpless in the ruins of a giant loading bay. Raptoria lasted only moments longer. Her shields were torn away by a sweeping blast of gatling cannon fire, and her speed was no protection from a volley of Apocalypse missiles that flattened an area a kilometre square.
Cavalerio felt their deaths and watched through the Manifold as Deus Tempestus sensed them too. Blood poured from his ravaged flesh and the liquid in his casket was almost opaque with it. He pushed himself to the front of the tank, feeling the fluids pouring from cracks in the glass and seeing the smoking ruin that was all that was left of his cockpit section.
Kuyper was dead, his body slumped and on fire in his moderati's chair, while across from him, the steersman, Lacus, was little more than a mangled lump of torn flesh. Cavalerio couldn't see his sensori, now realising that the entire upper section of the cockpit was open to the sky. The enginseer who had replaced Magos Argyre, an adept named Thunert, was still alive, only his lack of flesh saving him from the fires that swept the cockpit.
Cavalerio fought down his anguish as he saw the triumphant Aquila Ignis stride towards him, its colossal tread shaking the ground.
Its guns were silent and Cavalerio knew why, feeling the spiking pain of skitarii breaching charges detonating against his engine's leg armour.
'Mortis wants to capture us,' he said. 'I can feel them crawling inside us already.'
With what remained of his connection to the Manifold, the Stormlord linked with the enginseer's station.
'I do,' agreed Thunert. 'Though it goes against all my teachings, the alternative is worse.'
'Then do it,' ordered Cavalerio. 'Disengage all reactor safeties.'
'It is already done, Stormlord.'
'May the Omnissiah forgive us,' whispered Indias Cavalerio.
Seconds later, Deus Tempestus was utterly annihilated as her plasma reactor went critical with the force of a miniature supernova.
The death of Deus Tempestus was almost the last act in the battle of the Magma City.
Almost, but not quite.
That honour was saved for the city itself.
With the destruction of Legio Tempestus and the death of the Knights of Taranis, the last real opposition to the forces of the Dark Mechanicum were gone. Legio Mortis skitarii poured into the city through the smashed ruins of the sub-hives and landing fields, killing any soldiers they came across and capturing as many of the city's adepts as was possible at such a frantic, bloody time.
The scattered remnants of Melgator's army rallied to the snake-headed banner of a Mechanicum warlord named Las Taol, and surged into the city through gates now virtually undefended. The slaughter was terrible, and such was the frenzy of destruction that the bulk of the Dark Mechanicum forces did not realise their peril until it was already too late.
Artillery fire continued to pound those few areas of the city that still resisted conquest. The ground rumbled and buildings shook with violent tremors, but it was no gunfire that caused these tremors.
High on Aetna's Dam, the sluice gates of the Arsia Mons caldera locked into the open position, allowing vast, overflowing streams of lava to pour down the aqueducts and into the lagoon. Normally, this process was precisely regulated, but Adept Zeth had removed that control, and the magma lagoon began filling with lava straight from the heart of the volcano.
Far below the street level of the city, the void-protected columns that plunged deep into the bedrock of Mars to support the island of the great forge were exposed to the molten heat of the magma lagoon. The power that continually replenished the voids had been cut and the liquid rock began eating into the adamantium columns. The process began slowly at first, then accelerated as more of the inner core of each column was exposed.
A groaning crack boomed like the thunder of the gods, and the despoilers of Zeth's city paused in their debaucheries and looked to the skies in fear. The great silver road before Zeth's temple split apart and vast geysers of lava spouted upwards as the southern tip of the city broke free.
Towers and temples collapsed, their structures torn and twisted as the city heaved and buckled. The shriek of tortured metal and splitting rock were like the city's death scream, and its violators echoed it as they now guessed the danger.
Glowing lava poured in mighty waterfalls from shattered aqueducts, and rivers of blazing rock oozed through the streets, consuming all in their path. Altered skitarii and warp-enhanced Protectors perished as they were swept away by the searing tides of molten lava.
Soon the city was ablaze from end to end, the magma incinerating anything flammable and melting anything that wasn't. In moments, thousands were dead, attackers and inhabitants both, though such a death was a mercy for the denizens of the Magma City.
The Typhon Causeway cracked at its midpoint, a kilometre-long slab of rock shearing away from the city and tipping more than ten thousand men and war machines into the lava. Wrenched and torn by quakes wracking the city, the Vulkan Gate, which had guarded the entrance to the city for a millennium, fell and broke into a thousand pieces.
In the age to come, these would prove to be the only things to survive the cataclysm.
Thousands streamed from the city through the wreckage of the landing fields where Tempestus had made its last stand, but such was the overflow from the shattered aqueducts that no escape was possible. An ocean's worth of magma spilled outward, and the heat and fumes soon overtook those few who could outrun the lava.
Only Aquila Ignis escaped total destruction, Princeps Camulos turning and marching at flank speed to avoid the tide of molten rock. Even he was not quick enough, the lava flowing around the Imperator's mighty legs and steadily burning through its shielded plates. Aquila Ignis waded through the lava for five steps until at last its armour failed and its ankles gave way.