2 of my players have made a habit of blackmailing rather than turning people in to the Inquisition (e.g., nobles partially involved in cults). This is now gotten ridiculous, as they want to force these people to pay for creating a manufactorum for special ammunition.

I'd like to right the ship of state and have one of their "victims" turn them in in exchange for immunity (he'll probably get executed anyway), so now they're on trial themselves. I don't want this to end in their execution or imprisonment or being kicked out of the inquisition. What could I do to end this blackmailing thing without ending their characters?

Have their employer wthdraw support, or have a rival inquisitor use the player`s actions as evidence of their employer`s deviance and have him "retired" pending a full accounting of their actions.

Even easier just have the guy copping the plea bargain go to the arbites, have the other victims arrested and remove the whole setup for this horrendous exploit. This way you might even get the imperial authorities placing a bounty on the PCs as rogue agents.

Always remember that even though the inquisition has unlimited power its individual agents don`t. A simple method of nipping this in the bud would have been making blackmailed NPC call the players bluff and force the PCs to kill them or even just to commit suicide. After all you can`t menace favors out of corpses and even people in the imperium wil take notice after a dozen or so people suddenly turn up dead having last been seen with your PCs.

2 of my players have made a habit of blackmailing rather than turning people in to the Inquisition (e.g., nobles partially involved in cults). This is now gotten ridiculous, as they want to force these people to pay for creating a manufactorum for special ammunition.

I'd like to right the ship of state and have one of their "victims" turn them in in exchange for immunity (he'll probably get executed anyway), so now they're on trial themselves. I don't want this to end in their execution or imprisonment or being kicked out of the inquisition. What could I do to end this blackmailing thing without ending their characters?

Well blackmailing minor heretics is the bread and butter of many inquisitorial cells.

The idea being that you're using this resource to defeat greater heretics, and then coming back to mop up the little ones after.

So it's not really something you'd likely need to 'end' out of hand.

You could always assign them to even bigger heretic hunting, and see how well they fare with their 'allies'. (And if those 'allies' survive it.)

Operating a manefactorium is going to require a lot of paperwork. Licenses, contracts, inspections, etc etc. This is the Administratums turf, and these things take a lot of time, patience, money and bureaucratic expertise.

If they go by the book, perhaps they can start production in a century or so. If they try to use their Inquisitorial status to rush things, or to make pesky officials stop asking difficult questions, they will get Noticed.

Noticed is bad. Think burned spies. All the heretiks they chase will know of them, and the very crazy ones will have a new target for their spectacular suicide-bombing runs

It sounds like your players want to play Rogue Trader instead. Let them off the hook with a slap on the wrist and see just how far they'll go. If my players orchestrated an infinite money machine I'd be more impressed than anything.

If it's really, really out of hand consider this:

The Inquisition doesn't really have an "Internal Affairs Bureau" to counter excess, since each Inquisitor has extremely broad authority derived directly from the Emperor Himself. That doesn't mean an Inquisitor's agents have that same authority, though. One of your Inquisitor's rivals (also an Inquisitor, but could be an IG General, IN Admiral, Magos, Cardinal, etc) might have directed assets to watch the PC cell (among others), to gather evidence of corruption or moral turpitude, in order to undermine your Inquisitor's standing in the Conclave (which would be embarrassing for him, possibly lethal for the PCs for colluding and not destroying heresy).

Or, possibly, your own Inquisitor maintains a high-ranking "Internal Affairs" cell, whose job it is to ensure all his cells operate reasonably above board and turn over names of low-level heretics so they can be kept watch on to lead agents to bigger fish. if they find that none of this has been reported, that could turn the Inquisitor against the PC cell, with…probably some pretty unpleasant results.

And as for consequences…something like a penitent crusade. "Use your own money and wits to destroy the ork infestation on Olga VII. Succeed or die." Would be pretty epic if they succeed, or a great death if they do not.

The Inquisition doesn't really have an "Internal Affairs Bureau".

On topic, I also wouldn't punish the players bady. Maybe a fine, reduction in freedoms, having a bomb collar placed on their neck for one session, etc etc, is more the route to go. Truly depends though on how vile the crimes were they overlooked, how much those "bad guys" kept doing illegal things behind the PC's back, and what they were extorting them for. A minor Xenos artifact smuggler getting blackmailed for funds isn't so bad. But letting a demon summoning sorcerer go, learning dark secrets from him, and not keeping an eye on him which allowed him to cause more havoc, might be grounds for the bomb collar. Just saying.

Edit: You obviously can combine some these concepts to what other people have mentioned. The penitant crusade sounds very intriguing too. I like you style.

The penitent crusade sounds like a cool possibility but can easily turn into a multi-session adventure. If you're ok with derailing the main story for a while, it could be a nice change of pace

2 of my players have made a habit of blackmailing rather than turning people in to the Inquisition (e.g., nobles partially involved in cults). This is now gotten ridiculous, as they want to force these people to pay for creating a manufactorum for special ammunition.

I'd like to right the ship of state and have one of their "victims" turn them in in exchange for immunity (he'll probably get executed anyway), so now they're on trial themselves. I don't want this to end in their execution or imprisonment or being kicked out of the inquisition. What could I do to end this blackmailing thing without ending their characters?

Ever thought about letting them stand on trial, being dismissed by their inquisitor (with a considerable fine) but then being recruited by a more radical inquisitor. This way, you add some consequences to their behaviour, but keep them in the inquisition.

Furthermore, the radical inquisitor could impose certain limits to their power, but could also encourage your acolytes to continue this behaviour, perhaps even on a higher level.

Personally I wouldn't end this behaviour. That would be a waste of a perfectly good opportunity for a GM to have the PCs wriggling on a hook, smug in the knowledge that they put themselves there.

Step One. Don't stop the activity. If anything allow the PCs to get some pretty significant material benefits from it.

Step Two. Expand. Ensure that more and more bad guys are on the PCs books. Some of these guys are actually pretty high ranking in various increasingly sinister and malevolent cults. All are able to offer the PCs further high ranking cult members and material rewards to save their own sorry skins.

Before long the PCs are turning a nice profit and have mapped out a good section of the cult activity in the area.

Step Three. Things start unravelling. Adeptus Arbites, Enforcers and independent bounty hunters start investigating some irregularities. For example the manufactorum that was set up was only approved because unbeknownst to the PCs the noble murdered an administratum official who was obstructing the planning procedures. Now the noble wants help in delaying the investigation.

At the same time another cult leader or cold trader is having problems with an even worse threat, say a khorne mutant warband and asks that the PCs devote resources to destroying it.

No doubt the PCs think these actions are ok to protect their position, after all it is only pulling rank a little on some Enforcers and killing mutants. But the wider picture is they are becoming the patrons and leaders of the cults they are running.

Step Four. Ends Justify the Means.

The pressures of keeping all the blackmails, informants and off the book deals on the go begins to grow. The cult leaders contacts etc start making increasingly bold actions to advance their own position on the basis that there is a cell of acolytes protecting them.

For example one of the cult members informs the PCs that there is a particularly mad sorcerer in charge of his group. If he could be deposed of it could be a great victory for the Imperium. Of course it would also give said cult member a chance to advance. The PCs again cross a line, now they are justifying influencing cult politics to advance their own contact.

Step Five. Increase the Pressure. Rising undealt with cult activity has come to the attention of their Inquisitor. He wants results and asks the PCs to team up with another acolyte group (preferably this can include new PCs) to deal with the issue. How do the PCs decide which bridges to burn? How do they deal with these loyal untainted Acolytes. Whatever they do they’ll lose influence and potentially expose themselves.

Step Six: Corruption. A cult leader or xenos smuggler aware of the PCs predicament offers them resources to help them keep ahead of their master. Perhaps a sorcerous technique for scrying or heretical technological device that can alter data records.

The PCs are now running their own cult(s) and are directly opposed to the Inquisition. And they’ll be wondering where it all went wrong.

And that my friend is Dark Heresy.

However that said a few courses of action spring to mind to end the matter.

1) The guys being blackmailed are in fact Inquisitorial Acolytes belonging to an enemy Inquisitor and the whole thing is actually a sting operation. The tables are now turned and it is the PCs are the ones being forced to betray their masters

2) The nobles who are members of cults might call on their cults for support. Facing the wrath of the Inquisition might be just the tipping point needed to turn a hesitant cult member into a full blown initiate who is willing to sell his soul for protection. Perhaps a few weeks later the PCs start getting plagued by a daemonic assailant (maybe even a daemon host) trying to uphold its side of the bargain.

3) Depending on how heinous the crime the noble calls in favours to get him off the hook. Sure if the noble is full on calling up daemons only other cult members will help him but if say he is taking a share of a fairly minor xenos smuggling ring or even a member of a cult which is dodgy but has only been revealed to be outright heretical by the PCs there might be wriggle room.

E.g Noble goes to his brother who is of course the local Bishop and 'confesses' his sins. Bishop is willing to grant absolution on completion of 'very arduous' penance carried out under supervision of course and or the Bishop agrees to declare that the noble was working under his orders to infiltrate a potentially heretical cell in the city and the whole thing was a misunderstanding.

Basically the noble might go public and be able to survive by the skin of his teeth because of his connections.

The Acolytes on the other hand likely only have the protection of their Inquisitor which is now undermined because of their activities. Even if the Inquisitor allows for their transgressions they have made a powerful enemy in the Noble family.

Finally as has been said before I wouldn't necessarily think that blackmailing such low level cult members is such a problem. It depends whether the Acolytes are furthering the aims of the Inquisition or simply making a profit.

(Apologies for my previous post. it was quite long and I didn't review it before posting so the steps in my cunning plan don't add up. Two step three's no step two or four. For some reason it isn't allowing me to edit. I know I put a lot of typoes in my posts but I can count...honest)

EDIT: Fixed now.

The Inquisition doesn't really have an "Internal Affairs Bureau".

Actually, they do. They are just very few of them and very very secretive. Can't remember their organizational title though.

That is what the Ordos Malleus used to be. They were originally a secret section within the Inquisition with the job of containing daemons (as they still do) and policing the Inquisition from within. But this was way back when when whole regiments were executed and Space Marines mind wiped to keep the secret the existence of daemons, and even most Inquisitors were not really meant to know of their existence. Now the Ordos is pretty much just "That section of the Inquisition that deals with daemons."

2 of my players have made a habit of blackmailing rather than turning people in to the Inquisition (e.g., nobles partially involved in cults). This is now gotten ridiculous, as they want to force these people to pay for creating a manufactorum for special ammunition.

I'd like to right the ship of state and have one of their "victims" turn them in in exchange for immunity (he'll probably get executed anyway), so now they're on trial themselves. I don't want this to end in their execution or imprisonment or being kicked out of the inquisition. What could I do to end this blackmailing thing without ending their characters?

Well, if they are taking the time to set up these "rackets," then they are not doing their jobs. That sort of thing gets you in trouble with the Inquisition. They'd likely be executed if caught since that's how you get fired by the Inquisition. If you don't want it to end that way, have them put on some sort of penance. They remain a cell, but get the toughest assignments - the Inquisitor's way of testing their worth. They either succeeed or die trying.

I think most of the important things have been said (a manufactorum would take too long, another inquisitor is going to notice what's happening, etc)

Though I think you just need to talk to your players and tell them they're acting ridiculous. They're thinking of getting special ammunition...why not just demand the goods, rather than the equipment to manufacture it?

That's where they got out of control, they're not thinking like smart crooks (IE, acolytes), they're thinking like video game players.