Here is my Garvel Loken backstory.....

Sgt Garviel Loken looked down at the fallen Eldar champion that he just beheaded with a piece of rusty razorwire.
Loken's squad the Locasta had stumbled onto an Eldar ambush as they were holding the flanks.
The rest of the 10th were busy with the main objective which was to stop the refit of the Eldar titan before it became battle ready once more.
The bulk of the squad was coverering the right flank and Loken and four battle-brothers were covering the left when the world went black with an explosion of light and sound.
He awoke to find himself unarmed,his bolter and chainsword nowhere to be found and the Horrible sight of an Eldar beheading the last of his four man squad.
In a rage of fury he bellowed,"Kill for the Dead," and smashed into the Eldars back with the force of a Landraider breaking through an ork shanty.
A quick chop of his hand crushed ones windpipe and well placed kick split anothers head like a boromelon.
The Fourth Eldar would not be so easy with the advantage of surprise gone.
The two traded blows that could level mountains for the better part of the hour with niether able to land the killing blow.
Then like a thief in the night the Eldar disappeared.
After a frantic search he found the Eldar working on opening a small webway portal,if he succeded renforcements would get behind the 10th and crush them between the two Eldar forces.
Loken broke into a sprint and grabbed a piece of razorwire from a splintered tanktrap.
The Eldars armor and speed would prvent him from dispatching him quickly with his bare hands and he needed to end this quick.
The Eldar was about to press the activation rune when he had the odd sensation of falling.
He saw his armor five feet away as if he was having an outer-body experience,He noticed the massive body of the Marine staning over the headless body with a piece of gore covered wire.
He tried to cry in rage but found nothing but gurggles springing forth from his severed vocal cords and everthing went dark forever.
The battle was over that day and the 10th returned to the Vengeful Spirit.
Loken recieved word that he was to report to the bridge which was a first for him.
He had no idea the capt of the 10th died that day of battle wounds while in the apothacarrions care and that he was chosen to be his successor.

Very good, a nice way of expanding Loken's storyline from the Heresy books. :)