I have listed a few possible ancient astartes conspiracies and how they might affect the recent M41 -situation. The cool thing about these are that they go, so to say, "Beyond the Canon", so while there is material that hints to the possibility there is actually nothing that would outright say how the things really are... as always, I am interested in any comments, suggestions and feedback you might have

Imperium Secundus

Canon facts: During Horus Heresy while writing Codex Astartes Guilliman had a contingency plan called "Imperium Secundus". The real contents are not known. After Horus Heresy Guilliman became the Lord Commander of Imperium, Codex Astartes became the standard guidebook for almost all Astartes and more than 50% of all chapters come from Ultramarine geneseed.

Ancient conspiracy: What if it was Guillimans intent right from the start to let the other legions bear the brunt of fighting against Horus, save his own legion and establish his own lineage as the ruling elite of the "Second Imperium"? So Codex Astartes was not written to make Space Marines more effective, but actually to castrate the fighting power of other legions by fragmenting them and to reinforce the status of Guilliman himself by forcing everyone to play by his "playbook"... Then, while acting as Lord Commander, Guilliman made certain procedural adjustments to the way new chapters are created to ensure that his geneseed would be used in future. Guillimans full plan was probably never realized in full as he was poisoned and put into stasis, but his genetic and spiritual legacy forms the basis of vast majority of all Astartes still.

How to use: If this was even remotely true it would probably be one of the most horrible secrets in the whole Astartes community and any Ultramarine (not to mention any other Codex chapters who would know of it) would be ready to do ANYTHING to keep it a secret. Hell, since exposing this kind of ancient treachery would risk renewing old conflicts between Ultramarines and descendants of other legions and thus pose a huge risk to the Imperium itself even High Lords of Terra would be inclined to keep the secret firmly buried. Of course there is also the possibility of some sort of "Shadow Council" of Ultramarine descendants that still try to work out the old plan and control the destiny of Astartes and Imperium behind the scenes...

The Darkest Angels

Canon facts: Dark Angels have their secrets. A lot of them. All related somehow to their old Horus Heresy civil war. Dark Angels believe the Fallen are scions of Chaos and all corrupted. Accordingly the interrogated Fallen claim that Fallen are the "true heirs of the legion" and Forsaken are the traitors who purposefully left the Emperor alone not taking part in Terra conflict.

Ancient conspiracy: What if Lion was hedging his bets and purposefully kept his Legion back from the Terra with the idea of first seeing who wins (Horus or Emperor) and then joining the winning side? What if after Horus dies and Emperor is disabled and incommunicado Lion is still "playing it safe" and purposefully left his Legion divided so as to make sure his genetic legacy will be preserved no matter who comes out in top?

How to use: If this was true then it would probably be something very, very few know about. Maybe Lion and whoever was working with him actually spread two conflciting "truths" to the two parts of his legion. Maybe no-one knows about the original plan anymore and both Fallen and Forsaken work exactly according to what their primarch wanted, without even realizing it anymore. Or maybe there is a small "inner circle within inner circle" that keeps the conflict between Fallen and Forsaken going but limit it so that Forsaken can never kill off all Fallen...

Space Shark Mystery

Canon facts: Space Sharks/Carharodons operate outside Imperium and all Imperial control. There is no sure knowledge on when or why they were created and whose geneseed they come from (Raven guard is strongly suspected). Earliest notes of them come from 888.M32 which means they must be either 2nd or 3rd founding chapter. Raven Guard has a "dark secret" of having used cloned marines during aftermath of Istvaan catastrophy.

Ancient conspiracy: What if Carharodons are not of any official founding at all? Maybe they are, so to say, the "Black Templars of Raven Guard Legion" meaning they are the part of the Raven Guard that did not accept Codex Astartes? To keep up the appearances Corax removed these guys from the Legion before adopting Codex Astartes and gave them enough equipment from his former cloning facilities to secure that they could store and implant their own geneseed. Maybe even their original equipment is gathered from what was left from the cloned Raven Guard abominations when Corax put the abominations to the sword.

How to use: If this was true it would make the Carcharodons a true "self-made chapter" originally of no founding at all and answerable to no-one else. And they would probably know it but try to keep it secret. Also, if it was possible for "self-made chapter" once, is there any others of such out there?

This is great stuff.

Although the second one would seem to have been closed off by the last story in the recent 'Age of Darkness' anthology.

Fantastic stuff.

I think I shall be making use of the first two, alas there are no Raven Guard in my games KT but the other two, particularly the first, will give me endless hours joy messing about with Astartes brainpans.

Sounds awesome what about some more?

The Most Favored Son

Canon Facts: Horus was the Emperor's most favored son, and thus by extension the Lunar Wolves the Legion of Choice. Horus was made Warmaster and the Emperor suggested that Horus change the name of his Legion to reflect himself in it. Though few voiced outrage, the brother Primarchs of Horus did not agree with the fact that he was chosen over them.

Ancient Conspiracy: Rogal Dorn and by extension his Imperial Fists were extremely jealous of any who received attention from the Emperor other than himself. For was he not the only one in charge of an interstellar empire when Father found him? Was he not the one who could build defenses like no other? Was he not the one who held back his brothers when they were going excessive? When he had discovered that Lorgar had turned to worship father as a god, he was incensed. This after all was something he had already known, but dared not declare for it could upset father. To be sure, he put a negative spin on it and made sure that Father knew...and that the Ultramarines would help teach the Word Beaers a lesson. Then Rogal could help his brother Lorgar in his time of need...and send him on the journey that would **** him and eventually...**** Horus. Sadly, his convulted plans and conspiracies did not include Father being hurt. Just that Lorgar and Horus would both be destroyed and that Rogal would be the hero...and the next Warmaster.

Even today, few Imperial Fists know the heretical truth about their Primarch's plans. Those who do, continue with his plans at making the Imperial Fists and their line the most favored of the Imperium. This has resulted in other Chapters being manipulated into falling to Chaos, fighting losing wars, or accidentally being set upon Imperium targets to look guilty.

How to use: If this is true, then any Chapter who has gained plenty of glory or honor would be at risk from being involved in a plot to destroy them so that the Imperial Fists seem better by comparison. This has resulted in a long standing shadow war between the Imperial Fists and the Ultramarines and all of their lines though few really know the truth and even fewer would admit that this is happening.

vastrix said:

Enter Astral Claws and how the events that finally ended in Badab War were set into motion because High Lords withdrew support from Lufght Huron in order to support a certain Black Templar crusade...

Other ideas:

Pick a little-known more recent founding Chapter. The Alpha Legion infiltrated its command structure a few centuries ago, and have been continuing to do so: Either switching out established members for their own, or pulling aside aspirants and indoctronating them. And of course: Promoting their own to positions of power. Pretty much the entire Chapter's senior figures are now all technically traitors, and the Chapter's hypno-conditioning has been subverted, with a few secret command phrases buried in there, making the Chapter's troops effectively conditioned sleeper-agents. For now the Chapter continues to serve the Imperium utterly loyally, giving no hint of their secret, and the plan is to continue doing so for a few thousand years more in order to build trust. And then? Who knows? Perhaps the entire legion will turn traitor at a key moment, in a key position somewhere...

Blood Ravens being an off-shoot loyalist Thousand Sons Chapter is now pretty much as close to canon without being confirmed as such as it's possible to get, but it's a good storyline.

Likewise, the Space Wolves have a long history of wiping out other Chapters at the E's request. Before the 1KS it was pretty much stated that they wiped out at least one other Legion, and there have doubtless been many since. The Wolves could still be the Imperium's way of policing other Chapters, with a long and secret history of having destroyed dozens of them. It's not too much of a reach to consider that Guilliman knew their history, and tacitly supported their flouting of the Codex in order to ensure numerical superiority when purging other Chapters.

Canon Facts: During the Horus Heresy, Fulgrim joined Warmaster Horus in his rebellion, but during the events of the Dropsite Massacre he killed his closest brother, Ferrus Mannus, and then allowed the sword's daemon take possession of his body in the thought that it would take away all of the pain of what he has done.

Ancient Conspiracy: According to what's been read, it seems that only Horus knew about the daemon that has replaced his brother and he died long before getting the chance to set this straight to allow his brother a noble death. Suppose a few Emperor's Children who were suitably shocked at the death of a Primarch were shaken from the side of Chaos during the battle. They continued to fight alongside their Father until the end of the Siege of Terra where they were forced to choose to leave his side in order to avoid damnation within the Eye of Terror. They hid out in the backwaters until the Second Founding and then created a new identity for themselves in order to continue to fight for the "Right" side. They have been searching for a way to drive the daemon out of Flugrim's body and transform him back into his original form once more. To this end, they have changed everything from their name to their style to their very gene-seed in order to bring up more psychic potential in order to best combat daemons. Knowledge of their quest was eventually shared with the most selective of circles within the Inquisition who agreed to help bring a Primarch back to the "Light" (so they can crucify him or champion him...depending on the Inquisitor). This Chapter has faced much in persecution from the unknowing members of the Inquisition, and even purged of most of it's membership when their secret was leaked into the wrong hands. In fact, much of the living marines now no longer know who their Primarch is or what it is their sacred quest is. Hmm?

How to use: If this is true then of course the Blood Ravens make pretty good candidates for this. Or someone else...once the secrets to their past is unlocked then the quest for redemption will begin again. To discover how to get Fulgrim out of a painting and back into his body. Perhaps the daemon prince must be tricked in some way. The road to redemption is perilously close to the road to damnation and the Inquisition is watching...with no vested interest in helping unless Fulgrim can help them in some way...

This might be too obvious, but the Vault could have any number of items of great importance dating back to the disapearance of various Primarchs, such as one of the items that Vulkan supposedly hid. Were the Salamanders to find out what would they do to retrieve it? At the same time, the Deathwatch obviously needs the item as it was released into their hands by the Vault and so must have a dreadfully important use.

Or maybe the corpse of a Primarch is found within, such as Roboute's. If Roboute is here...then who is that in the shrine of MacRagge? Perhaps a Primarch that Roboute is supposed to have killed but is famous for making miraculous recoveries and is supposedly tuly loyal to the Empire despite seeming to be one of the Traitor Primarchs?

Might be a little too obvious though.

This is all great stuff and wonderful ideas for a Deathwatch game. A great cheer for all contributes!

My addition: A certain Chapter has a heretical Grand Apochetary who thought that he, in his forbidden research which was carried out far beyond the eyes of his own brothers. For this he had tampered with the geneseed of his Chapter in an attempt to make it perfect and remove its present degeneration. Thus the latest of the generations of the Chapter has a geneseed polluted by the GA's meddling and use of forbidden science and experiments. Only time will tell when the horrific side-effects of this becomes clear and if the Chapter will tear itself asunder, or be torn asunder by their former peers, outrages over the sacrilageous treatment of the holy geneseed.

vastrix said:

Blood Ravens are already tied by at least four unsubtle hints to the 1KS, though.