Raphael of my homebrew chapter alongside some lore :D
The owls are a loyalist space marine chapter within the Pandamonium subsector. They are a Raptor successor founded in the 35th milleniun, chapter founding that would eventually become known as The Cursed Founding. A founding that was riddled with so many issues, almost every space marine chapter that came out of that founding had some sort of defect or geneflaw. The Owls were no different.
The Owls suffer from highly mutagenic geneseed. When implanted, it has a habit of mutating something within the neophyte. It can be something as minor as eyes being a different color, or not having as keen a sense of taste or smell to consistently producing acid that needs to flushed regularly lest the marine will eventually just vomit it all up anyway, or their bonemarrow exploding. As such, and seeing as how they have seen the inquisition purge other chapters from this founding, they have put themselves into censure.
The Owl's space marine combat culture relies heavily on stealth, infiltration, and disruption from the inside. Not many of them favor melee combat, rather ranged methodical methods.
Their culture within the chapter is heavily based around brotherhood and acceptance of one another. To the point where when the ten thousand marched the primaris reinforcements across the galaxy, they happily welcomed their new brothers. (Although, they about shat themselves seeing a few of the ten thousand)
They are largely atheistic, rather pledging service to the throne, but pledging their loyalty to their brothers. They dont take excessive joy in their duty as space marines, they see it rather as a job. A job that needs to be done. Nothing more *most of the time, some marines are the exception, not the rule.*
They recruit by stealing children, either infants from orphanages, homes, or toddlers they happen to find unattended just long enough to take. This is to raise the child as part of the chapter, so that for as long as they remember, The Owls have been their only family. Failed space marine novitiates are kept as chapter serfs. They do however have a superstition, that if you take a child from their home planet without anything to keep with the child, that is damnation, or at least severe bad luck for the child.
One of the biggest shames of The Owls, and what for a short time brought the eye of the inquisition upon them, was the fall of their homeworld, Atreus Beta. Atreus had a chaos cult on the home front, working just under the Owl's beaks. By the time it waw in full force, most of the world was done for.
With a heavy heart, the second chapter master, Lucius, ordered exterminatus of Atreus Beta. Dropping a virus bomb, and reducing Atreus Beta to a mere floating rock in space. Making the chapter fleetbased.
This was one of the greatest shames of the chapter, and enforced their tactics of infiltration, but now they brought themselves to not just do surprise assaults, but make their main goal to dissolve cults before they can get a proper foothold. They refuse to let another Atreus happen.
You will know The Owl's did their job, when you think nothing happened at all.







