The Chimera armored personnel carriers hit the landing zone at ramming speed, their drivers having made the calculation that deceleration was optional.
One of them caught an Emperor's Children warrior directly across the midsection, the vehicle's front hull taking him in the ceramite at full momentum. He did not dodge. He did not have time to decide whether to dodge. The Chimera's mass carried the argument, and the tracks completed it, and what was left behind on the ground between them communicated the outcome unambiguously.
The Noise Marines answered the Chimeras.
Their sonic burst cannons discharged in sweeping arcs across the landing zone, the waves they produced doing to armored personnel carriers what they did to individual warriors: bypassing the outer shell entirely, propagating through the structure into every component inside simultaneously. The Chimeras that took direct hits detonated from the inside outward in a manner that suggested all their contents had decided to occupy the same space at the same time. The Skitarii Vanguard advancing behind them in the attack wave were caught in the overlapping fire and came apart in similar fashion.
The Emperor's Children read the engagement and found it unfavorable.
The landing zone was contracting. More defenders were arriving from multiple directions, and the open ground that had made the initial deployment practical was closing. Strange cries emerged from inside purple-red helmets as the warriors made the collective decision to break, and they activated their power armor to full output and moved for the gaps in the encirclement in separate directions.
What remained of the Raven Guard battle team, three warriors where there had been significantly more, stepped into the gaps they were responsible for with the composure of people who had already done the arithmetic. The Skitarii Vanguard, newly arrived and still reorganizing after their losses, pushed forward alongside them, attempting to contain the breakout before it became a penetration into the Forge World's interior.
They were buying time.
The Carcharodons arrived before the time ran out.
They came in multiple battle teams, moving through the Skitarii lines without slowing, the heavy footfalls of their power armor carrying ahead of them through the ground. From the power backpacks of their armor they pulled chainswords and chainaxes, weapons that came to full speed before the warriors were fully through the line, and they entered the fight in the specific way that Carcharodons enter fights, which is to say without ceremony and without stopping.
They moved between the Emperor's Children like current around obstacles.
Two or three Carcharodons on each target, cutting from different angles, their chainweapons working at the armor's weakest points while the target was occupied tracking the nearest threat. The warriors they killed dropped. The ones that didn't drop yet had chainaxe teeth embedded deep enough in their ceramite to make independent movement a secondary priority. The blood and the noise and the falling bodies were indistinguishable from the behavior of actual sharks in feeding water, and if the Emperor's Children who were still standing had any observations about the aesthetic resemblance to their own fallen nature, they kept the observation to themselves.
At one corner of the landing zone, three Carcharodons brought a Noise Marine down through coordinated pressure: chainswords engaging the armor's right side, forcing the pivot that brought the back of the Noise Marine's helmet into alignment with the storm bolter muzzle that had been positioned for exactly that angle. The storm bolter fired a sustained burst at contact range. The chanting that had been coming from inside the helmet did not survive the argument.
The Noise Marine fell in two separate directions.
The Carcharodons were already moving to the next target.
Time passed, and each increment of it reduced the Emperor's Children present on the surface. More Skitarii Vanguard squadrons came in from the flanks. More Raven Guard combat teams materialized from positions they had been holding patiently in the surrounding structures. The landing zone stopped being contested and became a compression, the Emperor's Children falling back to a section of metal bunkers and fighting from cover because it was the only option remaining.
There were fewer than ten of them left when the situation in the void became relevant to the ground engagement.
The Carcharodons fleet had not stayed in the docking cradles once its captains understood what had arrived.
Ships do not move quickly from fixed dock positions. The process of disengaging maintenance umbilicals and clearing the berth takes time even under emergency conditions, and the fleet's captains worked through that time while the orbital defense platforms and the Forge World's own Mechanicus vessels attempted to compensate for what the fleet could not yet contribute. When the Carcharodons warships did reach open void, they came out with weapons already cycling, and the combined firepower they added to the engagement against the Ark of Omen was substantial.
The Ark of Omen was larger than the combined fleet. It was not, apparently, more resilient in every location. The accumulated ordnance directed against specific sections of the stitched-together hull found seams between components that had been joined by methods not designed to absorb repeated heavy weapons impact, and one of those seams gave way.
A section of the Ark's hull separated from the main body.
The section was several kilometers across. Its trajectory, once separated, was determined by its momentum and by Triplex Phall's gravity, and both of those factors pointed in the same direction.
Carrier-based fighters from the Oberon-class warship scrambled and intercepted it in the upper atmosphere, firing continuously against the falling mass. The mass was adamantine-reinforced across its outer structure, and the fighters' weapons were designed for void engagements against targets without that particular property. They did not stop their attack. They also did not achieve enough cumulative damage to change the outcome before the falling mass cleared the altitude where fighters were effective.
Triplex Phall's anti-aircraft defense responded.
Hydra flak tanks rolled out of concealed storage bays in the foundry districts below, deploying in coordinated batteries that covered overlapping fields of fire. Hunter missile vehicles accompanied them, the Skyspear missiles they carried designed for exactly this category of target: large, descending, heavily armored, not performing evasive action. Dozens of vehicles took position across the industrial hive sectors and began firing simultaneously, the combined anti-aircraft network flooding the night sky with more ordnance than the polluted atmosphere could cleanly sustain.
The falling section broke apart.
Not into nothing: the Skyspear salvoes and the concentrated flak fire found the structural weaknesses in the falling mass and exploited them, fracturing the multi-kilometer piece into fragments tens of meters across, the reduced scale of each fragment making them vulnerable to the continuous fire in ways the original mass had not been.
Most of the fragments were destroyed in the upper atmosphere.
Most was not all.
The fragments that survived the descent hit the surface of Triplex Phall across a wide scatter pattern, each impact throwing debris and dust outward in expanding circles, collapsing the structures adjacent to the strike points and sending shockwaves through the ground that the foundry districts registered as seismic events rather than explosions.
The dust was still rising when the sounds started.
From inside the fragments, rising through the settling debris and the falling grit and the distant noise of the ongoing battle between the void fleets:
"Industrial axles intersect, sharp teeth that never cease in their consumption of flesh and blood."
"The hungry flames of the forge are howling; seeds are planted in the hot furnace; gold is refined and blood is boiled to create new life."
"Lock and key ring in the palm; candle and cold light illuminate the heart; abandon the old road and walk the road without rules."
"Where cables shine and twitch, steel is kneaded into flesh to form the blessed machine; grieving souls are bound by contract and do not escape."
"Look upon him and know him; your heart and soul are the more valuable for his regard; and he knows everything in the looking."
"The gear-daemon army has arrived at last. Vashtorr the Creator gives you his curse, and his omen."
The hatches of the landing fragments blew outward.
The cultists who stepped onto the ground of Triplex Phall were still chanting as they emerged.