If a Black Shield or member of a chapter whose main body is lost (e.g. Black Consuls) falls in service to the Deathwatch, what becomes of their geneseed? Does the Deathwatch ship it back to Mars for testing and storage? Seems unlikely with the tiny quantities involved. I'm more inclined to think they hang onto it in cold storage, in case brethren appear to claim it.

Another possibility arise: off the book space marines. The Deathwatch ranges far and is secretive even by Astartes standards. They have access to huge quantities of medical lore, recruiting worlds and secret facilities. And they always need more space marines. I think if not official policy, then I wonder if some Watch Commanders have not used at least Black Shield geneseed judged pure by the apothecaries to create completely black ops marines. Trained from childhood by some of the finest space marines in the galaxy and indoctrinated to know nothing else but loyalty to the Deathwatch. Having to pretend they are mere vagabound Black Shields themselves is a minor matter compared to the honour of finally serving the Deathwatch "in the open", or they could remain a completely seperate task force based on some lonely Watch Station. The risk is likely not worth the reward but I can see how a Watch Commander would both be tempted and see opportunities to actually pull this off.

Decessor said:

It's my guess that the Apothecary will ID the origin of the gene-seed, since they know every Space Marine's code; it's one of their honors to know such things, and keep such secrets till death. If the team has a Black Shield, I'd assume they will figure out where it came from (Chapter), and return the gene-seed to them. The Chapters can send stuff to Mars. Successor Chapter members whose Chapters have perished can have their's returned to the parent Chapter. If they got something nasty, like say one CSM out of the set wanted redemption in death, the Apo would ID that, too, and destroy the gene-seed, as it is tainted. As for Watch-made Chapters, I don't think they do that, personally. It doesn't really seem to fit into their fiction, needing to belong to a group, know their Primarch, blah, blah, blah. I could be wrong, of course, but I don't think they would make their own Chapters, as it would be hard to get permission from their home chapters, and if they didn't, that could be bad.

Watch-made Astartes are rare, simply because the few Watch Commanders who would do such a thing are few and far between. Radical or Codex Divergent Chapters may institute such an idea, provided they really are Divergent, but the majority of Chapters, being seconded from the Ultramarines Gene-Seed, tend to follow the Codex, and even if they don't still might consider that to be a relatively heretical act.

As to Black Shields and Doomed Chapters, it depends entirely upon the Chapter in question. Heretical Gene-Seeds are destroyed outright, or sent back to Terra to be stored alongside the Gene-Seed of the Traitor Legions. Dishonoured Gene-Seeds are sent back to their Chapter, if it still exists. Those Chapters that are dying have their Gene-Seed studied as much as possible, or they're sent to Terra for storage.

@venkelos

They don't know every space marine geneseed if only because not every space marine chapter tithes to the Deathwatch (they are uncommon but they exist) and it is also possible not every apothecary has access to all the relevant lore (the deathwatch is spread out pretty thinly). But yes, usually the black shield's chapter (or legion) will be uncovered sooner or later. I take issue with the notion an apothecary would automatically destroy traitor geneseed, since the High Lords of Terra keep vast quantities of Traitor Legion geneseed in stasis on earth. If the geneseed was actually visibly tainted by chaos, that's a different matter and could well be destroyed even before the apothecary gets to check it. I very much doubt even the most reckless or resourceful Watch Commander would be able to create a full chapter, what I was talking about was a relative handful of marines created from geneseed from known loyal Deathwatch marines. And there are a number of full chapters who don't know who their primarchs are (Storm Wardens an obvious example) so that is not necessarily a sticking point. That said, the theoretical black ops marines would need very thorough indoctrination or constant misdirection during their training to prevent them realising that they are not merely different, but a walking heresy.

@Darmort:

The Deathwatch as an organisation is noted to often stray from the codex astartes such as in customised battle formations and specialised wargear. But it would influence most marines thought. A few commanders might try, but that would leave a handful of black ops marines in the entire Imperium.

The trouble I have with this is that the proposed 'black ops' marines would be raw, untrained Neophytes, and pretty much a liability compared to a genuine Kill Team made up of fully trained and experienced veterans. Besides which, the Deathwatch is, itself, a 'black ops' organisation, so where's the real advantage? Anything that needs to be so desperately deniable would be best left to the Officio Assassinorum, who're less likely to screw up than the rookie blackshields.

With the level of Inquisition oversight the Deathwatch operates under (compared to regular Chapters anyway), I can't see unclaimed geneseed going unnoticed for long, and just how much geneseed are we talking about anyway? Just how many blackshields join the DW and then die with their geneseed intact and recoverable?

Personally, I think it's all just sent back to the Lords of Terra in the style of a tithe, if only to reassure them that the DW are loyal and not a renegades club. Sort of like the cost of taking on the blackshields, no questions asked, in the first place.

Dosn't it say in the rule book that the watch commander that accepts a Black Shield knows the Space Marines true Chapter? assuming the watch commander isn't dead I'd assume that he would let the relevent Chapter know about its Battle Brothers Death.