A Space Marine Chapter created for the Astartes Praeses position. You'd think the Imperium would have better records for a force tasked with something as important as guarding the doorway to hell. Supposedly they have very ornate armor and use a lot of purity seals. So an "official" version of these guys. Oh well, just another inspiration for the best Space Marine Chapter. From the name, they're probably Dorn's kids (stubborness, knights, like Astral Knights, Black Templars, etc.). The ornate armor and purity seals sounds like it would help bolster morale among allies. Each Marine a living symbol of the Emperor's glory and presence with his blinged out suit and fluttering signs of valor as he stubbornly murderizes the fuck out of everything stupid enough to cross his path. Oh, and they have illuminated stained glass windows on their armor.
Also, they have one of if not the most fuck awesome name of any Chapter.