|Homeworld||Vorl Secunda (abandoned after being nommed by the tyranids).|
|Strength||0. Completely annihilated by Tyranids in the middle of civil war.|
|Specialty||Defensive manoeuvers, trench fighting and all kinds of defensive warfare.|
|Allegiance||Imperium of Man|
|Colours||Red with black aquila and trim with silver aquila|
The Crimson Castellans were a loyalist chapter of Space Marines. During 995.M41, half of the chapter fell to the Ruinous Powers, starting a massive civil war. Finally surrounding the traitorous elements of the chapter on the planet of Sephrax. Just when the battle between the two astartes factions started to reach its climax, the planet was invaded by Hive Fleet Jormungandr. How both of these factions failed to detect that a massive hive fleet was on its way to the planet it's not certain, but what it is known is that both factions stopped fighting each other and allied against the tyranids. Maybe they remembered they were brothers despite their differences, despite the fact the Crimson Castellans were knowingly allying themselves with Chaos Pirates, maybe they both thought than not being eaten into oblivion was a priority before fighting each other to the death. Whatever the reason, they tried to push the tyranids back, but their weakened forces were no match for Hive Fleet Jormungandr, which just spammed raveners, mawlocs, trygons and other bioforms. The Crimson Castellans's Chapter Master was eaten alive while the rest of the chapter watched in horror, unable to help him, and the leader of the Chaos Astartes just fled the fuck out of the planet and hid into an asteroid base. Just in time for his asteroid to collide against a massive bio-ship, being eaten alive in the process.
- Brother Arduk: A Crimson Castellan marine who served the chapter for sixty years before being called upon by the Deathwatch, Brother Arduk was a strong silent type of guy who never the less dispensed wisdom beyond his years, even hanging out with the deathwatch librarians more than the other members of his kill-team.
After their fight against Jormungandr, the Crimson Castellans are considered extinct, with the few remaining survivors absorbed into other chapters.