Ok, I've gonna call my fellow GMs now for a little hell to throw on my unsuspecting characters.

The situation is as follows. Its one Apostate and one Psycher who have just left Hive Tarsus, after causing some hell there, with the aid of the Alpha Legion. But the Inquisition knows they have boarded a certain merchant ship and will plot to take them down. Also notice that the psycher has made and broken a couple of pacts with daemons and so they are out to get her as well.

They plan to take over the ship and turn it into a pirate ship, what they don't know however is that the Alpha Legion has already sold the routes of the ship to a bunch of Chaos Reavers who will descend and board later on with little interest initially to work with them.

As far as I am planning thus far I have this:

- A cell of Inquisitorial Acolytes are on the ship to silently investigate for the two Heretics

- An Ecclesiarchial Witch-finder is also onboard with a retinue in order to hunt down the psycher after her exploits in the hive.

- There's an ultra-violent semi-heretical Imperial cult within the ship who won't take well to two followers of Chaos

- The Daemons will likely try some shenaningans, like possessing some darkholders or something in order to hunt down these guys, or cause some hell when the psycher uses her psychic powers

More ideas would be welcome to make this a scenario to remember.

You could, at the culmination of the intrigue/sabotage/slaughterfest/combat have the vessel be boarded by the Imperial Navy. (Maybe the Inq. acolytes have arranged for this to happen?)

Will the factions band together? will they go about surviving on their own? how will this affect the loyalists aboard the vessels?

There are many ways this could play out.

You could, at the culmination of the intrigue/sabotage/slaughterfest/combat have the vessel be boarded by the Imperial Navy. (Maybe the Inq. acolytes have arranged for this to happen?)

Will the factions band together? will they go about surviving on their own? how will this affect the loyalists aboard the vessels?

There are many ways this could play out.

Good idea. I could certainly use this although I'm afraid it might be to much with the both the reavers and the Imperial Navy joning the battle at the same time.

Well, there's always "in-transit" shennanigans - a ship at warp with someone on board that a major daemon really doesn't like is going to have all sorts of trouble with warp riptides, and even a slight gellar field bobble is likely to see something nasty slip aboard with murder in mind. Significant damage would force the ship to make an emergency transition into real space - wherever they end up being.

If the heretics are really good, perhaps they can make the witch-finder believe that the inquisitorial acolytes are the heretics of the piece? The Temple of the Saviour Emperor - chaos' preferred mindless blunt instrument since M.31

How are they planning to take it over? Presumably they don't have any significant force with them, and if it's a merchant ship it'd need significant refitting to be a real threat to enemy commerce.

Well, there's always "in-transit" shennanigans - a ship at warp with someone on board that a major daemon really doesn't like is going to have all sorts of trouble with warp riptides, and even a slight gellar field bobble is likely to see something nasty slip aboard with murder in mind. Significant damage would force the ship to make an emergency transition into real space - wherever they end up being.

If the heretics are really good, perhaps they can make the witch-finder believe that the inquisitorial acolytes are the heretics of the piece? The Temple of the Saviour Emperor - chaos' preferred mindless blunt instrument since M.31

How are they planning to take it over? Presumably they don't have any significant force with them, and if it's a merchant ship it'd need significant refitting to be a real threat to enemy commerce.

I agree and thanks.

But some daemons coming aboard soundsl like fun. I'm only sad that one of the the first characters didn't live to see this day. He was a Chaos Space Marine who had managed to earn the ire of a Daemonic Herald of Khorne. It would have been great to see the two of them in a full-blown face-off (only time it happened the Space Marine rolled like a god against a lesser version of the daemon and so triumphed over it). Definielty going to run with daemons running aboard after one of the Tech-priest's underlings goes mad and mess something up before they can kill him.

As for taking over the ship they are going to use suberfudge during the travel to corrupt key personal and place themselves and their followers into key positions to wreak havoc. Naturally there will be some complications to this but in all it would've been a solid plan, before I added complications.