Scout-sergeant Raphael of the Blood Angels earned his fame during the Ork invasion of Armageddon. Teams of scouts were dispatched into areas of the hive world heavily occupied by Ork forces. The scouting missions provided little intelligence on any enemy movements due to the unpredictable nature of the Ork force and so their mission directive was altered. The scout teams were ordered to infiltrate enemy encampments, free any slaves and hinder the Orks as much as possible before extracting during the chaos that they had created.
Raphael led his scouts deep into occupied territory, taking care to operate only under the cover of darkness. With so much Ork activity going on, there could be no telling what misfortune any wrong move would bring upon them. Ammunition dumps and other targets of high value were rigged with explosive charges that were detonated simultaneously to make tracking his team's movements impossible.
The sergeant had been informed that there was a group of Imperial citizens being held in an encampment nearby, detected by the long range scanners of the fleet in orbit around Armageddon. So far into their own occupied territory, the Ork leaders had become complacent and let many sentry towers fall into disuse. This allowed Raphael's team to approach the encampment undetected with ease, covering their tracks and taking out any stray Orks randomly patrolling the area or sentry towers that were being manned. Any single casualties that Orks found laying around this far into their own occupied territory were common place - it is in their nature to challenge each other and make displays of strength, often without their opponents even being aware. Thus, bodies strewn around the encampment attracted no attention to the presence of the scouts.
Raphael's team remained in place around the encampment for two days, picking out weak points and gathering as much information as possible about the Imperials being held within the central compound as well as what Ork forces frequented the area. A member of the team reported that there was in fact an Ork general running the compound who had taken many high profile officials as captives, including a tech-priest.
Through a daring ambush, Raphael's team managed to sow confusion amongst the Orks, with Rapheal personally putting a sniper round through the right eye of the Ork general sending the others into a killing frenzy. The captives were slaughtered as well as the Blood Angels after the Orks had finally discovered the source of the precision sniping. The scouts fought with immense skill and martial prowess, but their light armour combined with the sheer weight of fire from the Orks brought down all but Raphael. The tech priest had escaped to the outskirts of the compound during the confusion, where the sergeant found him sabotaging a fuel line that the Orks had been using.
Raphael and the tech-priest were hunted down for several days as they made their way back to the hive cities still under Imperial control, managing miraculously to evade capture due to his extensive knowledge of stealth strategy. The tech-priest was able to provide the Imperial forces with vital knowledge that proved instrumental in the elimination of the Ork threat on Armageddon for the time being.
Captain Titus saw the opportunity to recruit the lone scout-sergeant into the ranks of the Deathwatch after he had proved himself against impossible odds. Since he had single-handedly changed the balance of a large part of the war, it seemed fitting to Titus to not only make him sergeant of a Deathwatch scout squad, but also to bestow upon him the title of Deathwatch Kill-Marine. On several occasions thus far, Raphael has proven himself invaluable in his role as kill-marine and is a solid member of the kill team.
Well that was very long winded but I hope whoever reads that enjoys it! I chose sergeant Raphael because it is stated here (
http://wh40k.lexicanum.com/wiki/Deathwatch_Kill-marine) that scout sergeants "often make superlative kill-marines".
Good luck with building the fluff for the other members!