Trooper Merrick slid the output control on his lasgun to maximum. He could still hear the words of the quartermaster when his platoon were issued with the Sibian VI Pattern weapons: “Keep the output slider set at standard. Any more and you're likely to burn out the emitter assembly.” He didn't care. Any moment now a force of Traitor Marines were going to be cresting the hill that his trench overlooked and if he had any chance at all of breaching their armour he needed to increase the power of his weapon.
In the last few minutes the ambient temperature had increased by twenty degrees. If Merrick had for one moment taken his eyes off of the ridge of the hill, he would have seen that the sky had clouded over. With a crash of thunder the rain started to fall. So heavy was it, that view of the guardsmen's targeted area became indistinct.
Minutes passed and the rain didn't ease. Then they came. Slowly. Heads rising above the hilltop, then shoulders, chests and legs. Walking, not charging, the blue and gold armoured Chaos Marines approached the trench. With the traitors moving this slowly, Merrick thought, he and his fellows may just stand a chance. Lasfire erupted from the trench. Trained guardsmen aimed at the weak points on their enemy's armour, visors and joints. Then the Archenemy opened fire.
The poor visibility didn't seem to be hampering the accuracy of the Chaos Marines. By the time their first volley was done, fully half of the guardsmen in Merrick's section of the trench were dead. Guardsmen began diving for the bottom of the trench to avoid the withering bolter fire. Merrick wasn't the first to hit the dirt but he certainly wasn't the last. He needed more firepower. He switched his lasgun to full auto. More shots in a shorter length of time meant he didn't have to expose himself to enemy fire for as long. He steeled himself ready to stand up and fight. As he looked up he saw the monster. The Traitor Marine loomed over him. It slowly raised it's boltgun to meet Merrick's face. The guardsman rammed the end of his weapon up under the Marine's chin and fired.
The top of the Thousand Sons Marine's helmet exploded outwards and with it a coarse black dust. The dust fell and settled on Merrick. All of a sudden, the trooper could see all the failures he had ever made in his life. He saw all the people who had ever loved him and how he had hurt them beyond words. He saw how due to his weakness, his comrades would all die, suffering horribly. He saw through time how his actions on this day would lead to the fall of the Imperium itself. There was only one way to save mankind and that was to end his own life.
He raised the muzzle of his las to his forehead and pulled the trigger. However, the last spurt of fire from his gun had burned out it's workings and rendered it useless. Culim, the guardsman to Merrick's left and his long-time friend, tackled him to the ground. He tore the affected trooper's weapon from his hands and tossed it aside. He took his canteen from his webbing and used the water within to wash the dust from Merrick's face and hair.
Merrick looked at his friend realising how close death had just been. Then he remembered the battle and how if he was going to live, he must re-join it and continue to fight. But without a weapon, how was he going to do this. Then, on the lip of the trench, he saw it, the fallen Traitor's boltgun. He grabbed it. It was old, but seemed to be in working order and loaded. Merrick stood up to his full height, looking down the boltgun's sights over the trench. Immediately he found his target. He aimed at the Chaos Marine's throat and pulled the trigger. With a sound of tearing metal the muzzle and barrel of the boltgun folded in on themselves. Merrick could only stare as the components that had previously been at the front of the weapon emerged from the back. The boltgun fired. The shell entered Merrick's cheek. Then his head exploded.
Trooper Culim wiped his friends brain and skull off of his face and continued to fire.