Shock at the death of such a magnificent machine rendered the defenders immobile for a heartbeat, but that was all the Mortis engines needed. As the Ordinatus was consumed in a sea of roiling plasma, the opportunistic Warhounds darted forward and smashed through the crumbled remains of the defensive line.
Amongst the defenders, the Warhounds barked their triumph from carapace-mounted augmitters and began the killing. Mega bolters blitzed and chewed up exposed soldiers in a furious storm of explosive rounds through which nothing could survive. Turbo lasers incinerated flesh and melted armoured units as the cackling beasts crashed the tiny figures that stood before them.
Drank with slaughter, the Warhounds raced onwards, crashing the few pitifully burned or shredded survivors as their slower pack members stomped over the walls between the worker habs and outerworks of Adept Zeth's mighty forge, as easily as a child might step over a fallen branch.
In the close-packed confines of the sub-hives, the Warhounds snapped and killed like hunting raptors, guns rippling with fire and their horns screaming with the elation of the kill.
One engine worked in solitude, methodically reducing block after block of habs and forge temples to rain with its weapons and bulk. Walls broke apart, smelteries collapsed and great coolant towers were brought down in tumbling cascades of rockcrete and steel.
Two others worked as a pair, one demolishing buildings with concentrated blasts of fire, while the other raked the rabble to slay any survivors. Together, they left a wake of destruction such as had never been seen in the Magma City's history.
Dust billowed in vast clouds and the sound of collapsing structures overpowered even the cackling glee of the Warhounds as they cleared a path for the larger engines.
The solitary Warhound was the first to die.
Its crew never saw its killer, but its sensori felt the auspex lock a fraction of a second before its voids were blown out in a devastating volley of las-fire and it was obliterated in a rippling series of missile impacts.
The other two Warhounds felt its demise and furiously surged into the rains in search of its destroyer. Darting forwards in a series of loping bounds, they came upon its smouldering carcass and swept the area with aggressive bursts of their targeting auspex.
The lead engine caught a return from behind a shattered steelworks and opened fire without waiting for a lock, hoping to drive its quarry into the open where its twin could finish it off.
The ironworks dissolved into a mist of pulverised rock fragments and shattered steel, but instead of forcing the engine behind it to ran, it had the opposite effect.
Lunging though the fiery debris, a towering monster in cobalt blue armour came at the Warhounds, its fists blazing and a heroic challenge issuing from its warhorn.
Deus Tempestus crashed into the astonished Warhound, smashing it to the ground and stamping down hard with one enormous foot. The smaller engine was crashed like a tin can beneath the mighty Warlord, the First God Machine of Legio Tempestus.
'Engine kill,' said Princeps Cavalerio high up in the liquid depths of his amniotic tank.
The second Warhound fled at the sight of the larger engine, turning and sprinting for the support of its fellows like a bully confronted by a gang of his former victims.
It ran straight into the guns of Metallus Cebrenia and Arcadia Fortis, who caught it in a lethal crossfire that ripped away its voids and gutted it in a furious hurricane of turbos.
Behind the two jubilant engines, the Tempestus Warhounds, Vulpus Rex, Raptoria, Astrus Lux and the Warlord Tharsis Hastatus moved into position within the hab-blocks, ready to defend the Magma City against the might of Legio Mortis.
Surveying the smashed wreckage of the slain war machines, Princeps Cavalerio smiled.
From the Chamber of Vesta, high atop the silver pyramid in the centre of the Magma City, Adept Zeth read the inloaded data of the four destroyed Warhounds. The arrival of Tempestus two nights ago might have prompted her to believe in the providence of the Machine-God, but she knew she owed her city's continued survival to Princeps Cavalerio's honourable heart.
Even without the terrible threat of the Mortis Imperator, the Tempestus engines were dreadfully outnumbered and outgunned, yet still Cavalerio had come. Had he not been interred within an amniotic tank, she would have hugged him in a rare outburst of emotion.
The first blow had to be struck from ambush in an attempt to even the odds, and though Zeth keenly felt the loss of so many soldiers and artillery, their sacrifice had been necessary to lure the engines of Mortis in with the promise of easy kills. Four Warhounds and a Reaver was an impressive tally, but gun for gun and engine to engine, Tempestus was still grossly outmatched.