Black Crusade is one of the more interesting settings, for many reasons which were already mentioned here. Thematically, if I were to run something like a Black Crusade game, I would probably handle it like this: Firstly. It needs to be decided if this is a 'Space Marine' level event. There are few ways to tie in a coherent story where half are space marines and the other half are normal. It either marginalizes the true awe-inspiring nature of the Space Marines (chaotic or Deathwatch or otherwise) or marginalizes the relative 'normals'. You could probably do a Deathwatch kill team with an Ordos Xenos Inquisitor, and you could probably have a token heretic of some kind with a band of renegade marines. And that will enhance the story in some ways because the lone exception throws a greater emphasis on the unique themes. But I would never (and have never) allow, for example, an Inquisitor team with a space marine as part of his retinue. Some players embrace this kind of thematic clarity, some get very upset by it. But there's a reason Space Marines rarely (if ever) show up in say, Gaunt's Ghosts books. Secondly, It would probably be best approached from one of two main premises: A) You are all in service to the same Lord - and are most likely either all Khorne, all Slaanesh, or perhaps Chaos Undivided. If you were Space Marines, you would belong to the same Legion, unless Renegades. You are actively working to further his agenda. B) You are all antagonists - set against each other in some system of ever fluctuating demonic alliances and betrayals. Not unlike the Black Library book 'Daemon World' by Ben Counter. Thirdly, any prospective BC GM has to sit down and really get a handle on what kind of story they're going to run. I don't think Chaos as a theme lends itself well to the same kind of story structures that Inquisitors or Rogue Traders do. In many ways, Inquisitor is the easiest story to tell of all. Anyone that has read Dan Abnett's Eisenhorn or Ravenor series will know what to expect, and it's easy to put a characterful team together. Rogue Trader is a bit more diluted...It's a bit more about amassing resources and has the same freedom of Inquisitor but without the same laser-focused goals. It's a bit more introspective, and attempts at forcing action in the story can sometimes come off as strained unless part of an intricate and logical series of events. It's safer to say that Black Crusade is to Death Watch, what Rogue Trader is to Inquisitor. It's somewhat similar in that the focus is on the most crunchiest aspects of the 40k universe. At least if you're playing in groups where there are multiple Berserkers. But at the same time, Black Crusade suffers from not having the beautiful simplicity of a Death Watch campaign. I could run a great Death Watch campaign that was basically a series of episodic kill-team like encounters. Then there's down time between missions, and then onto the next. And if a character dies, he gets replaced, and if a character gets too absurdly powerful, he either returns to his Chapter or acts as a mentor. You can't really do that with Black Crusade. You need to find a hook that gives people an excuse to go after some greater objective and not have to fight the most realistically Chaotic response to any kind of 'team' friction which is 'Screw y'all, I'm goin home!' or else, a murderous fight to the death. So you need to either embrace that, or find an immediate reason why that's not the case. Finally, the one thing Black Crusade has going for it over all the others is that Chaos lends itself to the most epic kind of stories. Not that an Inquisitor team or a Deathwatch team can't get caught up in the death of a world or a major sector war...but it's hard to imagine a Chaos Space Marine or Arch Heretic involved in a scenario where at the very least, a planetary-level struggle isn't involved, just as a starting point. Combine that with the fact its essentially a skirmish-level game of a dozen miniatures or so at a time (at least in real life). It also depends what kind of Roll20 game you want to play. Are you expecting every game on Roll20 to be a maximum crunch fest with tokens, squares and dice and new terrain every session - or are players equally happy with having like a map up, and plotting various meta-strategic movies, and then zooming down into the face-to-face action when appropriate. There's also the fact that its impossible to run any kind of crunchy WH40k game with skype and webcam without it turning very jokey, very fast. Funny as all hell, yes. Particularly compelling story crafting...no. There is going to have to be an overarching story frame, too. You can't just drop players onto the grid with a mission briefing handout, ala Deathwatch, and have it all make perfect sense (i.e, Brother Ajax spent thirty cycles in meditation and cleaning his chainsword...He's ready to kill orks again). Black Crusade, to be compelling, requires at least an intricate a narrative as Rogue Trader. ----- TL;DNR - Black Crusade requires a greater thematic clarity and uniformity of expectations between players and GM, moreso than any other setting
