Erikon Gaius glided into the heart of Spire Gamma once more.

The last time he'd gone here, it was on a reconnaissance mission; the last time he'd gone here, he had been sent by the Arbites to solve a criminal problem. He had solved it, diplomatically.

But did diplomacy even have a place in this brave new galaxy? The cult's actions were such that Gaius doubted even the renewed Imperium would approve of them. Dealing with Terra was, however, no less impossible than dealing with the cult.

Gaius' gunship was shot at as it headed towards the spire, even as it sent salvos against the makeshift batteries in the buildings' windows and on the Hive-streets' surfaces. Gaius' vessel rocked, sending into flight all objects not tied down.

"Head toward object 1-Zeta," the Captain ordered.

The pilot, Tactical Sergeant Caton Loppones, followed his superior's orders. Banking sharply, buffeted by winds of fire, the Thunderhawk leapt into a gap between two hab-blocks and zoomed into the battery.

"They've dug in well," Battle-Brother Iliam Zaneteon observed.

"Indeed," Gaius assented. The cultists really had dug in well - better than expected, but then again they'd planned this.

They were humans going up against Ultramarines, however. In the end, that would be all that mattered, barring something stranger than barricades.

"Jump!" Gaius screamed, even as a fireball expanded in the gunship's side. "Loppones, drop us and retreat to the smoke layer."

The Thunderhawk's hull opened, and Erikon Gaius, Captain of the 21st Company of the Ultramarines, leapt onto the cracked plascrete. Squad Loppones followed him into the block ahead. A structure loomed ahead; it had once been a hotel, if Gaius' auto-senses were correct. Striding into it, the Captain kicked its door open.

What waited inside defied all his predictions.

Instead of a typical, or perhaps slightly decorated, lobby a yellowish cathedral met the Captain's gaze. A mustard-colored gas filled the titanic expanse. Incense burners and narrow windows lined the walls. Lines of feathers hung from the ceiling. It was an unnatural, opaque place. Gaius' stomach turned in looking at it.

Worse than the building itself were its occupants. Pink and blue fish-like flyers zipped rings around the structure. Birds unlike any Gaius had studied upon induction fluttered far above. And ahead, in the yellow distance, something from a fevered dream stood waiting.

"You will die, Erikon Gaius," it stated.

There was no way to describe the monster, for its body changed with every instant. But Gaius could still tell its general shape, as it kept an overall avian form consistently. It was a massive vulture, or perhaps a titanic raven like that on Corvus Corax' sigil. It shined blue, in clear contrast to the yellow darkness that dominated the rest of the temple.

It was two-headed. One head was eyeless; the other, Gaius could not properly discern. The figure itself wavered, as if it was a phantom who was to retreat upon daybreak; it was almost transparent, and the opaque smoke was visible through its back.

When its spoke, its tongues moved without its mouths opening.

"Here," the xeno said. "Soon. I have seen it."

"We are all mortal, monster," Gaius stated.

"That you are," it responded. "That you are." And then, as Squad Loppones rushed ahead, it faded with a flourish. "My debt is paid, Kartan," it said as it vanished, though Gaius had to strain to hear.

The yellow air formed a tornado as it swirled into the void the xeno's - or mutant's? - form left. As if incensed by their leader's disappearance, the lesser creatures above swarmed down into the Ultramarines' formation.

"Strike back!" Gaius ordered, though it was unnecessary.

Bolters ripped through the aerial assault, with startlingly little effect. A ray-like creature dove for Gaius' head, even as it burned from a shell's impact. Drawing his powersword in one fluid motion, the Captain sliced it in half. This time, it fell to the floor uncontrolledly and did not rise.

Another of the pests hurtled at the Captain's face, but Gaius responded with his Betcher's Gland, burning its wings off. The being continued its motion, allowing the Ultramarine to knee it into the depths of the hab-block.

Around Gaius, Squad Loppones copied its Captain in massacring the aerial fish. Bolters and chainswords, as well as a plasma cannon, turned the attack into wings and eyes. As the beasts' flesh was separated from their bodies, it melted into a violet liquid that achingly contrasted with the yellow surroundings before evaporating.

Within minutes, it was all over. Nothing was left; only an error-inducing combination of gases hanging in the air bore witness to the fierce attack.

"Casualties?"

"Battle-Brother Zaneteon is down," Caton Owaxetes reported.

"I'm still alive," Zaneteon noted, legs covered in the blood-like liquid. "We'll never beat them like this, Captain."

"Indeed," Gaius observed. "Meet up with the other units at the epicenter. Theoretical: if we take out the leadership, the creatures will lose cohesion."

No one questioned the theoretical, though everyone saw it was far from being an unimpeachable guarantee of victory. This was going to be a pitched battle, however, and to minimize casualties the Ultramarines would need to take any possible shortcuts they could.

Otherwise, Astartes would die here. The avian's words stuck fast in the Captain's head. Did the beast have some form of prophetic psychic talent? Was this to be his last battle?

Had he cleared his doubts only to -

Gaius chuckled at the irony of the situation. Here he was, doubting. He had always known he would die eventually; and this battle, at least, was just. Courage and honor; that was the whole point.

The Ultramarines filed out of the altered building, and Gaius led them at a jog towards the building that had contained the temple during Gaius' last descent. The smoke- not yellow, here, but rather darkly multicolored - pulled closer around him here. In terms of illumination, it was night, though by Gaius' chronometer Carenn's sun should not yet have set.

Gaius led Squad Loppones through chipped and collapsing buildings. In one ring of walls, abandoned from the inside - where had all the people gone, anyway? - a small orb of light exploded the opposite door, wreathed in furious fire. "You are nothing!" it screamed, before being disintegrated by a neat shot from Owaxetes' bolter. Were there hallucinogens on the wind?

The Ultramarines' run faded into a march, rhythmic footsteps shaking the plascrete apart. Gaius twitched as he remembered the collapsing scaffolding from earlier in the day; that had been dangerous, and he dearly hoped that Spire Gamma was sturdier than it looked.

"Break march," he ordered, but the shaking didn't stop.

Gaius saw Veteran Sergeant Ionnases from a distance, as a blue smudge in the overwhelming fog. The suit's autosenses gave his position as less than five hundred meters away, but the power of the fog and the buildings that still dotted the landscape were sufficient to blur the Devastator Squad, even to Astarte vision.

Nevertheless, Gaius pointed his group towards Ionnases, ordering a meet-up through the vox. Every squad's and group's news was the same set of odd skirmishes, but the Ultramarines were now contracting in a ring around the epicenter temple.

Then, suddenly, it fell into view.

It was powerful, intimidating, a work clearly meant to impress. It achieved that purpose. It was red and brown, covered in beating wood; there were corpses on the walls, a display of incomprehensible barbarism.

"And those are citizens of Ultramar?" Assault Sergeant Hardonisses voxed.

"They were," Sergeant Partaxen said with uncharacteristic bitterness.

"Practical: Meet up at my position," Gaius ordered, "and break into the wall."

Assent was heard in response, along with a lot of static. The net was breaking up; no surprise, given the oddness of the overall endeavor.

"Theoretical:", Hardonisses suggested, "perhaps the enemy is assisted by the warp-creatures we were war - kktch - out?"

"Practical: We know of no specific way of fighting more effective against Warp-spawn, except the power of psykers. Which we don't have access to. Just kill them."

"How can Warp ent - kktch - the Materium?"

A brief debate followed, interrupted before its time by the vox-net finally collapsing in its entirety. Then there were only footsteps, slowly converging into a hundred and forty Astartes ready to end the madness at its core.

Veteran Sergeant Orsono came up first, his helmet glaring. His Squad was with him, weapons ready for the practical. Then other Squads began to pull up - Marianes, Frazant, Xelarcal. The last to come were Partaxen's Devastators, covered by Thespates' Assault Marines. By the time they reached Gaius, those Devastators present were already hammering into the temple's back wall.

There was the briefest of warnings before they broke through; odd brown lights on the living wood, one Gaius initially took as sap of some sort. But then the wall fell, and the chamber within was revealed.

It was, as Gaius had expected, debased. But the manner in which it was such shocked even him. The large hall held thousands of corpses, whether stabbed, choked, or drowned. Many of them had civilian workclothes on; indeed, they had to be civilians, because there probably weren't this many Arbites on Carenn.

The mound of bodies was highest towards the center of the square room. Above it, there was a hole in the ceiling large enough to accommodate a Thunderhawk; a multicolored miasma surrounded the pyramid's summit, leaking upward to create a veil of smoke. Even as the Ultramarines watched, a ring of humans- mutant humans - danced on the mountain of corpses, chanting something in a non-Ultramar language that strained Gaius' ears.

"Attack them," Erikon Gaius ordered.

The Astartes aimed their guns -

And then there was an explosion of brilliant light. For a moment, Gaius saw nothing, and then he witnessed a titan stride out of the fog.

It was crimson-skinned, and massive - not quite as big as one of the Mechanicum's war machines, but as big as, say, Roboute Guilliman. Its face was bestial, with a constant grimace; its feet were hooved. From its back grew leathery wings that dripped a liquid Gaius recognized to be blood - specifically, human blood. All in all, it was as a bat, though with a bull's head and legs. It certainly had a bat's arms, hairy and small.

The monstrosity swung a black blade, one that seemingly appeared out of nothingness, and pointed at the Ultramarines.

It roared.

The building shook, dropping pieces of masonry onto helmets and flesh. Two of the ritual's circle were hit by one large piece, immediately falling down dead. Battle-Brother Anstallo of Squad Partaxen, too, was knocked into pulp by a direct impact from a massive piece of plascrete. Chunks of at least that scale pattered the beast, but it continued moving forward.

The Ultramarines opened fire. It roared again, this time in pain; but that did not stop it - moving unnaturally fast - from jumping into the air, only to land onto Squad Thespates. The Assault Marines had tried to charge; but every one of them was either instantly flattened by the enemy's bulk or cut to pieces by its sword. Pieces of armor littered the floor; Sergeant Thespates raised his blade in an attempt to parry, but pure metal was instantly pierced by the black unknown, and the abomination killed the Ultramarine.

"I am Erkaggek!" it screamed. "And I will end you all!"

Had the avian been right, then? The Ultramarines were concentrating fire, and the xeno was weakening; but nothing seemed to be capable of destroying it. Another squad - Frasar this time - fell under the monster's blade.

Then, Gaius recognized, with an emotion a human might have called fear, that the ritual was continuing, that a new form was taking shape in the emerging fog.

"Concentrate fire on the humans!" Gaius screamed. "Deal with the Erkaggek later!"

The Ultramarines did so. Bolter fire ripped apart the summoners' flesh- was this how you made deals with Warp entities?- and, slowly, to Gaius' great relief, the form in the heart of the corpse mound faded.

But the Erkaggek attacked again, and this time Orsono felt its wrath. The monstrosity was weak now, slow, bleeding from a thousand wounds; but the Ultramarines, too, had been bloodied. The Erkaggek knew its end was near, and in its final agony, it decided not to go down quietly; in its dusk, as the miasma began to fade, the Erkaggek leapt at Squad Loppones.

This, Gaius knew, was what the avian had predicted. This was the end. The Erkaggek's blade swept in an arc, black edge homing in on the captain's throat…

And then falling to the ground, as its owner's head, far above Gaius, exploded in light.

There was a fireball. The wreckage of what Gaius recognized as a Thunderhawk gunship toppled to the ruined floor, harmlessly distant from the startled Astartes.

As the flames blossomed, a Space Marine, slightly charred, flopped onto the ground.

"Sergeant?" Owaxetes wondered, even as chunks of the Erkaggek's disintegrated head showered the ground below it with blood. Bathed in that blood, Sergeant Caton Loppones clambered to his feet.

"Captain Gaius," Loppones noted, "I must inform you I followed your orders to the letter. I did stay in the smoke."

And as Loppones emerged from under the falling debris, the fog began to lift. Slowly at first, then faster and faster, bringing light into the former temple. The creatures still within the hall screamed, sucked into nothingness along with the fog surrounding them.

Seconds after the Erkaggek's head was gone, the effect was over. The spire fell silent. Exiting the site of massacre, Erikon Gaius watched the streets, now empty of both monsters and men.

"We won?" Hardonisses asked via vox.

"No," Gaius said, his voice hard. "We lost. In allowing this battle to take place at all, we lost."