I'm new to GMing Dark Heresy, though I'm fairly familiar with the universe, and I ran into a question in my current campaign. I know that some technology, especially xeno tech, is heretical and would be very frowned upon by members of the Adeptus Mechanicus. That said, can some of the more common weapons (like a lasgun or chainsword) be made heretical in some way (maybe by the addition of a piece of xeno tech or the like). The question arose because I want my players to face some enemies who have weaponry that I don't want falling into the hands of the players, due to its powerful nature.

The players are coming to the end of the current story and have narrowed in on the head of the cult they are investigating. I was thinking of having the boss have a chain axe, but I don't want the guardsman of the party to pick it up after (something I'm sure he would do given the chance). Is there any lore that I could use to explain how he cannot use the chainaxe, because it would be heresy. There is a tech priest in the group who could identify the heretical nature of the weapon if need be. What would that nature be?

Any weapon that has been modified with non-standardized (Mechanicus-approved) designs would be considered heretical. If the 'Machine Spirit' was corrupted with profane symbols, that would count too. Blasphemous marks is a perfectly fine way to handle it (you could even assign it higher damages or pen, give them special traits, etc).

There is a methodology in the 40k universe to 'save' or 're-santify' such weapons (Ref: Calgar's powerfists). To deal with that, ensure that such a process is extremely arduous and unlikely to be performed easily by the parties tech priest. In fact, I'd say such a low heretical weapon would be below the Mechanicus' willingness to even attempt.

Or, if it's in the hands of xenos, make it gene-keyed to that xenos species and unable to be used by a human. Or if in the hands of a particular cult, they need faith in a particular Chaos God to use it.

If you want it to be more "shouldn't use" and not "literally unable to use," it can be corrupted by the Ruinous Powers (the cult patron) or whatever. If he REALLY wants to use it, slap him with some hefty Insanity and Corruption and call it a day.

Black Crusade has deamon weapons, though that's probably over kill for this purpose

Make crystal teeth for the chain sword, a good ol' 8 pointed star, some glowing symbols, obviously living components, the possiblities are endless.. Also you can make the weapons explode (or if you are feeling perticular cruel) make the boos explode in a burst of gore and guts.. or make it only respond to certain type of users...

But all in all, be careful. Remember that they are not spacemarines, or you can risk losing party memebers..

But all in all, be careful. Remember that they are not spacemarines, or you can risk losing party memebers..

If your acolytes don't appreciate every breath they draw, cherish every moment of sanity, revel in every day not being corrupted and mutated...you're doing it wrong. This is a lethal game and characters already have Fate Points as 1-up mushrooms.

The players are coming to the end of the current story and have narrowed in on the head of the cult they are investigating. I was thinking of having the boss have a chain axe, but I don't want the guardsman of the party to pick it up after (something I'm sure he would do given the chance). Is there any lore that I could use to explain how he cannot use the chainaxe, because it would be heresy. There is a tech priest in the group who could identify the heretical nature of the weapon if need be. What would that nature be?

Two options:

1. It's covered in heretical symbols and blasphemous script that's actively nauseating to read. Merely picking it up is good for a few corruption points. No, it isn't any more powerful than a normal chainaxe, it's just corroding your soul for no particular reason.
2. It can't be picked up, because it can't be put down, because it's not really an axe. It's just a chainaxe-head, pin-bolted into the stump of this guy's forearm in a crude mockery of a bionic. If properly chaotic, the flesh has started to grow back around it (albeit livid and black-veined) and a momentary spatter of torn flesh is kicked out every time he guns the motor. Lovely.
3. The ordos want the axe because it's evidence. One good general-purpose anti-looting policy is to remind the players that theoretically, their function is to enforce the law, and the people they're fighting are criminals. The criminal's property (especially weapons) are evidence, and the Ordos will want to impound and investigate them, and will take stuff off them at their debriefing if they don't surrender it voluntarily.

If he REALLY wants to use it, slap him with some hefty Insanity and Corruption and call it a day.

until some untimely mutation reveals his radical tendencies