What Is Even Happening

I have confirmed that I have a concussion. When we reached the space station after the evacuation, I reported that my squad was killed due to a crash landing to Canoness Van Heppel. Upon hearing this, shockingly, she assigned me and my haphazard group to a new mission. She even offered us a full run of the supplies for our mission. Unfortunately, it involved another dropship.
Once we landed, Fig informed us that there are other psykers and something “found” her. I will never understand how they do what they do. Its… unnatural… We arrived at the wall and made our way into the darkness below cautiously until we heard someone talking in the distance. Lenni moved forward with a flare to see if they were friend or foe. When Lenni lit his flare, we saw guardsman uniforms, but they were defaced with symbols of chaos. Heresy!
Lenni opened fire with his boltpistol and vaporized two of the filth immediately. Another began bleeding out of his nose profusely. Ovie took careful aim and fired but missed and hit Fig in the back. Gelt managed to pull Fig back to us so that I could attend to the wounds. Nearly lifeless, I pulled her back from the brink! My combat medicae skills kicked into high gear and I focused closely, pulling the bullet from the wound, stemming the bleeding, stitching the wound closed, and applying pain killers. With my help, she once again drew breath. THE EMPEROR BE PRAISED!
I moved up to the corridor and hugged the wall to the side just in case someone needed my expertise. 5 more guards appeared in the hallway. Gelt threw a flare and they screamed in agony as they were blinded. To contribute, I took aim and fired at one of our many enemies. Unfortunately, I am only moderately skilled in guns. Luckily, by the grace of the Emperor, they fell screaming to the ground. The last of our enemies are dead and bleeding on the ground.
Thanks to the guidance of the God-Emperor, we navigated the rest of the way through the wall. Outside the wall are thousands of deceased, untainted guardsmen. May their souls be at peace. Fig pointed to a glowing in the distance and suggested we head in that direction. On the air was the faint sound of ominous chanting. As we got closer, we determined that those who are able to use stealth and shadow should proceed. Gelt and I held back. Gelt then headed to one of the trenches and pulled up a deactivated servo skull. I will never understand the Mechanicum, their ways are foreign to me.
As I looked ahead, there was a naked and chained guardsman on an alter… I knew that was a bad situation. As I watched, the overseeing Chaos scum began cutting into the guardsman. From cover, I saw Ovie toss a grenade and in a bright flash, the alter suddenly exploded. I attempted to cheer her success but saw a chaos space marine attacking the three of them! Gelt and I moved to assist.
As we ran, at some point, Gelt lept onto the back of her servitor and rode it into battle. She began chanting… something… and opened fire. There was another explosion closer to the alter, but I have no idea what caused it. I have come to the conclusion that this group, while wildly unorthodox, is some of the most careless, reckless, and crazy bunch of individuals I have ever known.
The rest of the combat became a bit of a blur. I remember leaping at the cultists and... purging the lot of them. I have never experienced such clarity. It was as though the Emperor himself was guiding my hand. When I came back to myself, the sorcerer floated above us. His eyes gleaming with unnatural confidence. He conceded the battle but threatened to return and with a blinding light, he disappeared. Most likely into the warp from whence he came, the villain.
I am excited if a bit fearful of my experiences in the thick of the fray. I have only experienced combat in simulation. Never would I have imagined that it can be so invigorating. Is this how Lenni experiences delivering judgment upon the enemies of the Imperium? I should ask him.