Anyway, here's the story. Enjoy!
No one spoke as the lift descended into the depths of the hive. The four guards nervously flexed their fingers as they gripped their lasguns, which were pointed as best they could manage in the confined interior at the figure which stood in the middle. The figure stood half a meter taller than the rest of them, clad in a dark green robe over a black bodyglove. The robe's edges were worked with small letters in white thread that none of the guards recognized. He was motionless, his face partly hidden beneath a hood, and what could be seen was devoid of expression.
The lift clattered to a halt, and the door ground open on old gears. The two guards in the front stepped out, keeping their guns trained on the giant, who silently padded out. With all four guns trained on him, he walked steadily down the permacrete tunnel towards a larger set of door. Beneath his hood, he glanced from side to side, noting the traces of dried blood, and the crudely painted sigils of the Dark Gods, which matched those engraved into the armor of the soldiers around him. He felt a slight twinge in his mind to see the sigils, but it was a sensation he had long since become used to.
Two more guards stood outside the doors. One bore a lasgun, the other carried a gently steaming plasma gun which gave the area around it a pale blue glow. Their armor was worn, but distinctly ex-Guard. All traces of Imperial insignia had been long-since removed. The one with the lasgun keyed a code into a panel next to the door. Although he tried to keep his body between the visitor and the keypad, it wasn't hard for the visitor to tell from his arm movements what the sequence was. The visitor's mouth twitched slightly into a grin for a split second before vanishing.
The large doors swung inwards, revealing a modest chamber that may have once been used for industrial purposes. There were the ruined remnants of equipment and pumps, but it had been largely cleared out in favor of tables and hololith projectors full of maps and other tactical information. Many of the maps had been rolled up and the hololiths disabled, but the visitor's enhanced vision picked out a number of minor details anyway, and his knowledge of the deployments of these renegades grew greatly.
Within the room stood four more humans, flanked by a pair of Ogryns. The humans bore a mix of aristocratic garb and officer attire, and the Ogryns' faces were hidden beneath crimson hoods. They pointed their blunt ripper guns at the visitor, and one of the humans stepped forward. His uniform appeared to be that of a senior officer, though his carapace armor was now encrusted with spikes and embellishments proclaiming his new allegiance.
"Welcome, noble Astartes," he said with a hint of disdain in his voice. The visitor came to a halt, and slowly reached up to pull back his hood. His pale face was free of blemishes, though he had a single silver stud above his right eye. His hair was black but short, and his eyes were a piercing green. He glanced around, taking stock of the half-dozen humans and two Ogryns that had their weapons trained on him, before looking back at the general and nodding slightly.
"General Krozium, thank you for agreeing to meet with me. I am Brother-Codicier Helcate." He held his hands out to his side to indicate he was unarmed. They had already checked him several times on his way down, but it seemed a prudent choice anyway.
"Of the Lords of Oblivion Chapter, I believe it was." Helcate nodded in confirmation, and Krozium continued. "I must admit, I was surprised to receive word of your offer. I know full well how unwilling the Imperium is to negotiate, especially when it has lost."
Helcate gave a nearly impercetable shrug. "You have proven a most intractible foe, and, despite our best efforts, you yourself have been impossible to find until now." He noticed the guards stiffened slightly, as if expecting him to attack them. He didn't budge.
"If that's supposed to be a threat, I doubt you could survive long enough to kill all of us."
"Not at all, General. Merely an observation. Let us move on to terms, shall we? The Astra Militarum regiments here have been devastated by both yourselves and your daemonic allies, and only the Lords of Oblivion stand between you and total control of the planet. Defeating you is taking more time and resources than we anticipated, and we are needed elsewhere. The terms are simple. A mutual disengagement for one week, and by the end of that time, we shall be gone. Do you find this agreeable?"
"It's obviously some kind of trick," one of the other leaders said. The man was clad in the torn robes of an Archbishop, though lesions covered his skin and rot had half-destroyed the robes. Helcate had no idea if the robes were actually his or merely stolen, but his allegiance to the Plaguefather was obvious. The man gave a quick rasping cough and said, "They simply want to buy time to infiltrate deeper into the hive and make us complacent before they renew their attack."
Helcate raised his hands, palms outward, and smiled, "Come now, I know we are bitter enemies, but I assure you my terms are genuine. What would I have to gain by coming down here alone and unarmored?"
"A foolish move, I think," Krozium replied. "I agree to your terms, assuming you honor them, but, until we confirm your complete withdrawal, you will remain as our...guest." The guards tensed again, expecting violence.
If Helcate was bothered by the statement, he didn't show. "That was not part of the terms offered. Return me to my Chapter, and we will withdraw."
Krozium was equally unmoved. "No. You will remain with us for the next week. Perhaps you might even...learn some things to take back to your Chapter."
Helcate chuckled and folded his arms. "You really are stupid, aren't you? Not only do you think you can keep me here against my will for an entire week, but you think you mortals could corrupt me to the service of Chaos? I've likely forgotten more about the Warp than all of you have learned combined."
"This is pointless. We should just kill him, and rid the Astartes of a senior officer," a third leader spoke. She wore baroque armor as well that was a mottled red, likely stained that way more through blood splatters than actual paint. She held a power axe in each hand.
"She's right, you'd be better off just killing me. Or trying to, anyway," Helcate said, his amusement still obvious. His hands dropped to his sides.
"No, I want assurance they will hold up their end of the bargin. A hostage will go much further towards ensuring that than a corpse. Even if the Imperium returns later, we will have had time to consolidate our defenses." Krozium lifted his power saber and pointed it at Helcate. "You will make sure this happens."
Now Helcate laughed openly. The rebel leaders shifted uncomfortably. "By Ferrus, you're an idiot! You doomed yourselves the moment I stepped in here, but you're too stupid to realize it! Go ahead! Shoot me!" The guards hesitated, looking to Krozium for guidance. "SHOOT ME!" Helcate bellowed.
"Do it!" The woman screamed. The guards squeezed their triggers. Nothing happened. Almost as one, they looked at their guns, confusion spreading across their faces as their triggers refused to budge. The Ogryns grunted with exertion as they tried to fire their guns, but the triggers didn't budge. Krozium looked at Helcate, icy dread spreading through his heart. Belatedly, he realized the sensation of cold wasn't just him, but the air in the room was getting cold as well.
"What..." was all he could manage as Helcate drew in a deep breath and closed his eyes. When he exhaled, his breath came out as icy mist. His eyes opened, and they crackled with blue energy.
"You really thought loyal servants of the Emperor would genuinely negotiate with scum like you?" Helcate's voice was full of both lethality and amusement, and it echoed not just around the room, but within Krozium's mind. The guards and Ogryns all began to scream as they found their trigger fingers forcibly pulled away from their guns and then forcibly severed from their hands. The screaming only intensified when all of them began to clutch their heads before their eyes exploded, and they all collapsed to the ground.
"Kill him!" The priest rasped, and the woman charged at Helcate with a fierce scream. She swung one axe at his head, but the axe merely exploded as it hit an invisible wall of force inches away from her target. The explosion hurled her back. Helcate tilted his head back slightly, and the woman flew into the far wall with such force she simply disappeared into a cloud of blood.
Other than tilting his head, Helcate hadn't budged a muscle since he spoke. He took a step forward, and Krozium tried to take one back, but found his legs utterly frozen. He tried to look behind him to see what the other two were doing, but saw they had both collapsed to the ground as well, blood leaking from their eyes, ears, and noses. The screaming had subsided as all the guards died.
Helcate took another step forward, and came within arms-length of Krozium. He tried to lift his power saber to strike the Space Marine, but the blade flew out of his hand and clattered uselessly in a far corner.
"You have my gratitude, general. You've save us a month of trouble to find you. We would have found you eventually, but not only will your leadership fall today, we will learn everything there is to know about where the rest of you are hiding."
Blood began to leak out of Krozium's nose at the sheer force of Helcate's psychic presence. The Astartes raised one hand and put it atop Krozium's head. Despite the frost covering his armor, he screamed as white hot fire lanced through his mind, shattering his sanity as all his military knowledge was forcibly ripped out. In less than two seconds, the interior of his head was reduced to scorched ash, and smoke began to leak out of his ears as he collapsed.
The frost covering every surface began to subside, and the glow in Helcate's eyes faded. He walked over to one table full of maps, and quickly glanced over its contents. He turned away from the table after realizing there was nothing on the maps he didn't already know.
He closed his eyes and reached out with his mind, seeking another mind in particular. Once he found it, he spoke to it.
Captain Tiburin, the rebel leadership has been destroyed, and I have extracted full knowledge of their deployments. I am returning to the surface and will be back within the hour. Your plan worked perfectly.
He had to strain slightly to hear the reply, as the response was not being actively transmitted by a psyker.
Excellent. Well done, Helcate. I await your return.Helcate closed his psychic senses without a further word, and walked quietly from the now-still room.