OK, I just picked up the three books of the Apostasy Gambit for cheap (overstock at the local FLGS) and I want to put them to use, but… I don't play Dark Heresy anymore. My WH40k game of choice is Black Crusade. I'm looking for some tips on how this set of adventures can be flipped to play with a group of Black Crusade Heretics.

I've only started to read The Black Sepulchre, so I'm not sure quite where to start. I do know that having the PCs go looking for the daemon's hand (sure doesn't sound like a daemon prince to me - perhaps more of a herald) should be a fairly easy switch. I'm considering having the Inquisition raid occur at the same time just to set up a three way battle as the opening piece. I'm also pretty sure I want to move this scene to a world other than Scintilla - possibly Malfi.

OK, so I don't think I'll have a problem with Part 1 (the raid on the noble's estate), but Part 2 (the crawl through the cathedral) is looking a bit tougher. For one thing, it's really a terrible piece of work. The thing reminds me way too much of an early D&D adventure with a room-to-room crawl, but it gets worse from there. The 'mystery' element seems almost nonexistant. Further, aside from combat, almost every Test is more or less pointless as they all have the "if the characters fail, have this happen so it doesn't really matter that they failed" - yuck. Beyond even coverting it over, I'm not seeing how this section would be enjoyable to run as written, and that leaves me wanting to edit it out. Any suggestions on how this way used by others (traditional playthrough or otherwise)?

The map of the Cathedral and it's descriptions are not properly matched, so that is one thing you'll have to rework.

Many of the clues rely on context, and the GM has all the context (naturally, having access to everything). I noted that many clues parsed within such a short span of time or within the relatiely small confines of the Cathedral tended to muddy themselves and become less clear. The place is "haunted", the scenario using ghosts and ghost events to relay clues and leads, but these clues and leads (predominantly) rely on the Players understanding the relationship of one entity/NPC to another, and this is only completely revealed if you are the GM. First, I suggest deleted the Navigator bit altogether- unless you're of a mind to have the PCs return the remains to its Nobilite House for some token reward or service? Second, the links between each entity are weakly forged shorts that (I believe) were written after each encounter was placed: SPOILERS!!

Mad brain scientist experiments on poor victims, what remains of the victims is locked away, PC unlock and release victims, combat encounter ensues, clues are haphazardly placed that weakly tie mad scientist to other NPC entities.

It might be worth looking into running each installment of the Apostasy Gambit in a pseudo-reverse chronology. SPOILERS!! I'd make the assault on Thrung's estate the culmination of the scenario, with the reward being the Hand of the Dei-Phage. It begs the question: How do you intend to use the Malefactor's Hand, if at all? Or the duplucity and doppleganging of Cardinal Ignato? Or a Titan semi-possessed? Much of the trilogy's second installment is crap all important to the wider scenario- more mad scientists performing experiments? (sigh)

I think what you're attempting to accomplish, your intent, is a refreshing idea. But will require taking each scenario completely apart and having it reordered with completely new context. I'll spend some time looking more thoroughly through the Apostasy Gambit trilogy this evening, making notes, and share some of my thoughts in a few days.