It all happened so fast, even my mind could only focus on so much. 

I heard Emmaline's voice ring out and felt the power of her psychic gift burst forth. The cackle from Clara's submachine riddled the air. I was infected with tunnel vision, my eyes focused entirely on Vorn. The traitor had turned just in time to meet my wild charge. So quickly had this all transpired that I hadn't even the frame of mind to unsheathe my power sword.

Vorn recovered like a rearing snake, taking my first punch and rolling with it, letting the weight of the blow drive him into a counter strike. I shoved it aside before it took purchase, and the two of us struck, pivoted and kicked when applicable. Vorn attacked with furious strength, a wild look in his eyes with a barely suppressed snarl. His fists hammered into my arm as I blocked, and I fell to sweep his legs out from under him. He leaped, seeing the move a fraction too soon for it land. I rolled away from his falling knee, rising too quickly for him to take advantage. I dodged a blow and locked his arm, pressing a palm into his shoulder as my other hand pulled his arm out to the breaking point, but he spun and leaped, letting his body realign as he attempted to throw me to the ground with a drop kick. It struck my breastplate, but I altered my stance and held my ground, letting the carapace armor absorb the blow.

He went for a knife, yanking it out and stabbing at me with the alien surety of a scorpion's stinger, stabbing downwards. Unfortunately for him, I caught the knife on my armor's bracer and headbutted him in the face. He nearly fell headlong to the floor, but instead he just lost his knife from my wrenching it away, the blade clattering to the ground. To his credit, he did not seem too perturbed, instead he strode forward again, fists up, ready for more. He fought desperately and was growing tired, but still, he fought well. Almost too well. I had no doubt in my mind he was far older than I was, and thanks to either rejuvenant technology or accursed blessings by his masters, he was as youthful and hale as I was. 

But I had caught him at a moment of weakness, and I was better armored, and most importantly, I had righteous conviction. 

Finally, he feinted, and then lunged for the power sword at my belt. Only seconds ago had I realized I had it, so blinded by my mission. My mind worked quickly, and as his hand closed around the hilt of the weapon, I let him pull it out by a few marginal inches. I grabbed his arm with my left hand and struck him in the face with my right, my fist hitting his nose so hard I felt the cartilage shatter. The words 'die!' fumbled on his lips as he staggered, letting go of the hilt. I pulled it out for him, and with a swift stroke, the blade cleaved through his torso like a scythe through wheat. 

It was then, even before he even realized he was dead, before his body began to crumble in two, did I let myself view my surroundings. My blood ran cold when I saw the chaos marine towering over Emmaline, her power nearly spent and armed with naught by her staff. Even if I were an adeptus astartes, I would not reach her in time, and so I gambled. As Vorn began to fall to pieces, I spun, gripping my power sword and swinging it in a terrible arc before I let it go. The blade, thrumming in the air, flew end over end across half a dozen meters before the blade sliced through ceramite armor as if it were paper. The sword burst forth from the chaos space marine's chest like a lance of lightning, and quivered there as the traitor astartes paused in its mad laughter. 

I had followed the blade's arc, and seconds after the sword had sliced through the armor, I gripped the hilt. However, astartes were not killed so easily. With speed beyond what I thought he was still capable of, he spun and struck me with his elbow. The blow was powerful enough to send me and the sword flying back, skidding across the ground. Luckily the blow had hit me square in my breastplate, and merely cracked a piece of the armor. 

Still, the traitor marine was heavily damaged from that. Its breath ragged and its left hand pressing to the gaping wound. I got to my feet, blade up and eyes set. 

"You will not stop me! Lord Tzeentch has plans you cannot comprehend!" The astartes said, its voice reverberating from the augmented voice box integrated into its eldritch helm. 

"It is my plan that you die here and now. Make peace with your bitch gods," I said, my voice steeled as I moved to hold my power sword two handed, its blade pointed straight up in an archaic duelist grip. Suddenly, bullets sprayed at the traitor marine, ricocheting off its armor and drawing its attention. Clara let out a battlecry, and I charged in.