I was born on a backwater planet the Imperium had all but forgotten. The only thing I knew of the universe without was that the God-Emperor watched over me and blessed my family.

On my twenty-seventh birthday the Imperium of Man rediscovered my little planet. They told me the God-Emperor demanded a tithe and I was part of it. I left my home without a word. I knew my duty.

They gave me armor and a lasgun then dropped me on some foresaken rock I had never heard of with men I had never met.

The odd thing is I have no recollection of how long we were there. Weeks... Months... Even years could have gone by without my knowing it. The only things that were certain toward the end was that I was good at killing and the men to the left and right of me were my brothers.

One dark day on patrol we heard a rustle in some brush. Our advance was slow and careful.. It didn't matter.. I didn't get a good look at what hit us but whatever it was, it was big and it was fast.

I awoke some time later amongst the bodies of my fallen friends. That thing killed my brothers.. My rage took control of my logic. I found a trail and followed it. I would kill this thing or I would meet my brothers at the Golden Throne.

It was difficult to track with many twists and decoy routes through the brush and over the streams. I marched nonstop into the night. I was getting tired. My discipline was slipping. I stumbled twice but I kept moving. It had to die.

The early morning light was fast approaching when it happened. A moist warmth on my neck snapped my attention into focus. How had it gotten behind me? I had fallen asleep as I walked.. Just like the green-as-ork-dung conscripts the commissar uses for cannon fodder..

I knew what it wanted, why I wasn't dead yet. It wanted to watch the hope fall from me. It wanted me to admit defeat. It wanted to watch my sholders fall and my chin to touch my chest. I wouldn't give it the satisfaction. I stood at attention and awaited my death.

Suddenly a crack, pop, and the bright white-blue flash of a plasma pistol. There was a new warmth on my neck, the warmth of xeno blood. I stared into the dark spot left on my eyes from the flash. As the spot faded a man stood in its place who said to me, "I am inquisitor Nicodemus Victus Constantine and you work for me now." He has lead and I have followed ever since.

^^^ that's a short and to the point backstory for one of my groups PCs.