The Hellfire missile crossed the chamber in a flat trajectory and found Vashtorr's avatar at the junction of neck and upper chest.
The warhead was designed to defeat armored vehicles, and what it had been fired at was a construct of gear-work and condensed cable mass the size of a small building. The explosion filled the circular square with light that was not light in a conventional sense, the expanding fireball consuming the mechanical upper body and the interconnected structure below it in a cascade of detonations as the gear assemblies' stored energies released simultaneously. The shockwave that followed had no specific direction: it filled the chamber uniformly, the circular geometry of the space reflecting it inward from every wall at once.
Vashtorr's avatar had no time to respond.
The head came apart in the first detonation. The upper body, the curved horns, the flame-eyed face, the vast gear-work architecture that had given it form: all of it was mechanical debris in the air before any of it had registered the impact. The Chaos fire that had burned in the eye-apertures scattered into dispersing threads of orange-red energy that found no anchor in the newly destroyed structure and dissipated.
Then the melta bombs reached their moment.
Three hundred simultaneous detonations distributed across the floor of a circular space one kilometer across produced a thermal event that had no local equivalent. The mechanical debris already in the air from the Hellfire strike became metal vapor. The gear-array infrastructure that had formed the chamber's center, the power transmission core of a vessel the size of a small planet, encountered temperatures that its materials science had not been engineered to survive and responded accordingly.
The cables liquefied. The gear mechanisms, the housing structures, the ancient framework that had been the Ark of Omen's heart for however long it had been assembled: all of it became molten material, and the molten material became airborne, and the airborne material found every surface in the chamber including the surface of Nolan's vibranium power armor.
The armor's kinetic absorption capacity was working at its limit from the shockwave pressure already. The thermal load from the metal liquid contact layered on top of it, and the suit's surface temperature spiked past anything its external sensors were calibrated to measure. From outside, the vibranium shell disappeared under a coating of molten metal, the golden armor becoming something that resembled a humanoid shape cast in cooling magma.
The Warp portal behind him had not closed.
The Ten Rings, which had been knocked from Nolan's arms by the initial blast and scattered across the chamber, found him through the smoke and debris, returning to his forearms from four different directions simultaneously. His hands were not moving by his direction anymore. He was conscious enough to register that he was moving but not enough to know why or in which direction. The Ten Rings pushed.
He went through the portal.
The portal closed.
The circular square, the power core, the chamber that had held Vashtorr's avatar and three hundred melta bombs and the Primarch's last exchange with a Chaos entity that wanted to become a god: none of it remained in a form that could be called present.
The chain reaction did not stop at the chamber walls.
The destruction of the Ark of Omen's energy distribution core propagated outward through the vessel's internal structure with the remorseless physics of a pressure differential finding every available path. Bulkheads that had survived ten thousand years of service met the expansion wave and found themselves reclassified. The weapon arrays on the Ark's exterior, which had been engaging the Carcharodons fleet and the Mechanicus warships in the void above Triplex Phall throughout the boarding action, went silent first: the power that fed them was no longer being delivered. Then the internal spaces of the vessel experienced what happens when the energy infrastructure of a planet-sized mechanical construct fails simultaneously from the inside.
The Astartes who were still alive inside the Ark of Omen felt the ship beginning to die around them and understood what it meant without needing to be told. They activated what remained of their melta charges. The detonations they added to the chain reaction were individually smaller than what Nolan had set off in the core, but they were distributed throughout the vessel's structure, and distribution was what the chain reaction needed.
Above Triplex Phall, in the void where the void fleets were still fighting, something changed.
The Ark of Omen's weapons were producing fire. Then they weren't.
The silence from the Ark's weapon arrays was noticed by the fleet's gunnery crews before any formal report could be transmitted: gun batteries that had been tracking active targets found no further incoming fire and registered the absence. The Mechanicus fleet's auspex operators registered the shift in the Ark's energy signature. Seconds later, the vessel's hull began to produce light from the inside, the exterior panels first flickering with secondary detonations and then separating as the structural forces holding them in place were overcome by forces working from within.
The Ark of Omen, which had appeared in Triplex Phall's outer system as a construction larger than a moon, dissolved over the course of several minutes into a debris field that the void fleets would be cataloguing for the next several hours.
On the surface of Triplex Phall, the defenders looked up.
The Ark of Omen had been visible in the upper atmosphere throughout the engagement, its silhouette backlit by the exchange of firepower between it and the void fleets. Now that silhouette was changing, the edges of it losing definition, the light coming from it shifting from reflected weapons fire to something originating within the hull itself.
The ground forces of the Chaos invasion were still fighting when their support collapsed, and the defenders did not give them time to process the change in their strategic situation. The Skitarii advanced. The Carcharodons who had remained on the surface pressed from every available angle. The remaining cultists and daemon engine constructs on the ground found themselves fighting a losing engagement with no possibility of extraction and no vessel to extract to.
At the edge of a cratered battlefield, blue teleportation energy assembled from the air.
The Astartes who came through numbered forty-four.
They arrived carrying their weapons and their damage and their dead brothers' gene-seeds, and they stood in the dirty air of Triplex Phall's surface while the last of the teleportation energy dissipated, and they looked at each other with the specific expression of warriors who know the exact cost of what they have just done.
The Armiger-class Knight materialized beside them, Reditus reintegrating with the chassis at the same moment. The Armiger's armor carried the record of the last few hours on its surface: impact scoring, ablative material loss, sections where the refractor field's repeated activation had left permanent discoloration.
Tyberos arrived through the chaos of the ongoing ground battle with the Claws of Maelstrom still active, the lightning fields carrying the residue of whatever had last been in contact with them. He was not moving at full sprint, but the pace he had was not a walk either.
He stopped in front of the assembled Astartes and Reditus and looked across the group.
"The Primarch," he said.
The 3rd Company captain stepped forward.
The report was brief: the boarding had scattered everyone immediately on arrival. Those who had been with the Primarch reported that he sent them away before facing a Chaos Champion alone. The nature of the explosion they had felt through the Ark's hull was consistent with the Primarch having destroyed the ship's power core, after which the surviving Astartes had detonated their own charges and teleported. At the moment of teleportation, the Primarch's power armor was not within the barrier's coverage radius. The armor's life-sign transponder was not currently returning a signal.
The captain finished his report and held his position.
Tyberos did not move for two seconds.
Then one massive gauntlet closed around the captain's throat and lifted him, and the Claws of Maelstrom on the other hand rose with the slow, deliberate quality of something that has already decided where it intends to arrive.
"You lose the Primarch," Tyberos said, quietly, "in one boarding action."
The Armiger's mechanical arm interposed itself between the claw and the captain's neck.
The arm was not Terminator-armored and it was not Primarch-grade, but it was sufficient to interrupt the motion, and Reditus's voice came from within the chassis with the precise tone of someone deploying words as a structural element.
"Chapter law is not suspended because the situation is difficult, Chapter Master. Battlefield discipline has clear provisions for dereliction and for failure of duty, and those provisions exist so that the Chapter master does not act as an executioner on the basis of his current emotional state." The red eye-lenses did not look away from Tyberos. "And you know what the Primarch is capable of. He opened a Warp portal before we arrived at Triplex Phall from across the sector. Doing so again, from inside a burning ship, is not beyond him."
Tyberos held the captain for another second.
He understood the logic. He had been applying it to himself for the last thirty seconds and reaching the same conclusion Reditus had just stated, which was the main reason the claw had not completed its arc. He understood the Primarch's capabilities. He had seen what Nolan could do in situations that had no obvious solutions.
The claw came down.
The captain was set on the ground.
Tyberos turned his head toward Reditus.
"The two of us will pray to the Voidfather for the Primarch's safe return." The voice was not quiet anymore, but it was controlled. "But if he does not come back, Reditus: the Carcharodons will reduce this Forge World to bedrock. Because the fleet would not be here if not for this place, and this battle would not have happened."
He looked at the debris field in the upper atmosphere for a moment.
"What I promise, I deliver."
He turned, and the Terminator armor engaged at full stride, and he drove back into the front line of the ongoing ground battle without looking back.
The Armiger stood in the space he had occupied, its eye-lenses oriented at the void above.
"My Primarch," Reditus said, to no one in particular, in a register that was quieter than anything it used for communication. "Where have you gone?"