Death Spectres

Death Spectres
Battle Cry	Fear not death, we who embody it in His name!
Founding	Dark founding (13th)
Successors of	Raven Guard
Successor Chapters	None
Chapter Master	Unknown
Primarch	Corvus Corax
Homeworld	Occuludus
Strength	1000 (ish)
Specialty	Psykers, Resurrection
Allegiance	Imperium
Colours	Black with one white pauldron

An example of how when a Space Marine is told to stick to a task, they do so, the Death Spectres Space Marines Chapter have stood guard over the Ghoul Stars for roughly seven years or so (seven thousand in-universe). Hailing from the 13th 'Dark Founding', of which the only other chapters known are the Exorcists and the Crimson Sabres, the Death Spectres maintain this task without support from the larger Imperium. Because they're that badass.

What this means is these guys are hard enough to remain on the edge of the galaxy, kicking any random xenos ass that comes along, and they never think or need to ask for the Imperium's help. Not much is known about the creatures that inhabit the Ghoul Stars, but they are described as being 'supernatural', and were clearly a big enough threat once for a whole Chapter to be stationed in constant watch mode to make sure they never bother anyone again.

It is confirmed that they are Raven Guard successors, since they share the same geneseed mutations, but because no one in this damn galaxy knows where they are from and who their daddies are, this question will probably go on unanswered... until Steve Parker got sick of GeeDubs' enforcing the "make everything unconfirmed" policy on every single damn chapter, and had a Death Spectre librarian outright say he was a successor of the Raven Guard. So yes, sons of Corax all the way.

They get their aspirants to die then resurrect themselves using only willpower, and then if they want a promotion, they do it again. Their chapter logo is a skull with double scythes behind it, and their colours are black, with one white pauldron and a bone colored helmet. They're not really that well known, but there was a Deathwatch book with them in it and it's pretty badass. They've also got this glass chair (called the Shariax) that all the Chapter Masters sit on that kills them but gives them huge psychic power, so the chief librarian commands them while their boss is busy dying. According to the Deathwatch novel, the Chapter Master (Known as the First Spectre), does this because if they didn't, according to them, the Imperium at large would be royally fucked. What EXACTLY would happen is known only to the Death Spectres, and is considered their biggest secret. According to the novel, the Imperium at large doesn't even know the Shariax even exists, or that their Chapter Master is basically killing himself on it in order to prevent...something. Again, only the Death Spectres know what would happen if this isn't done, and they WILL not tell you about it unless you are another Death Spectre, but it certainly sounds an awful lot like a certain chair made of gold located on Terra. They've got all these Persian sounding titles like Mesazar and Megir.

Despite being on guard duty, they do get out and about and help out everyone else. They were last reported being all sneaky during the 13th Black Crusade and helping some Imperial Guard recover a planet, which sounds like very Raven Guard-ish behaviour....

In the short story "Flayed" by Cavan Scott, a few more things are revealed about them, they "save" people from their world if they are deemed to be prime stock, they are sent to a breeding world, we see this happen with the main protagonist in the book Alundra who is taken by the Death Spectres with many others from her world which is infested by Flayed Ones before they exterminatus the planet. They seem to do this because of the lack of colonised worlds between the ghoul stars,and main Imperium space and they may have a gene seed mutation that may cause them to have white hair, corpse white skin and blood red eyes.

Given the setting, though, it makes sense to have a breeding world full of people genetically predisposed towards being suitable for Astartes gene-seed. This would provide a consistent, large recruitment pool of superior quality recruits for a Chapter that most likely is sustaining frequent fatalities given their enemies and large area of operation without Imperial support. Really, it could be considered odd that other chapters don't do the same thing. (I believe it could be said that if multiple chapters started kidnapping people from worlds and made them into breeding slaves, the Imperium wouldn't be the happiest would view it as a great honor. Producing Angels of Death in defense of humanity would obviously be an immense honor and sacred work.)

There is also the question of the Rubicon Primaris. Since the only real difficulty of the operation is the dying part (pain means nothing to Astartes, but dead is dead) and the Marine must come back to life through a combination of heart stimulation and willpower. Willing themselves back to life is standard for Death Spectres, so turning into Primaris Marines would be easy for them.