I'm considering picking up Dark Heresy 2nd edition when it's released and GM a campaign. I've DMed D&D extensively, but I'm keen on something else. I'm somewhat familiar with the crunch and I'm quite familiar with the WH40K fluff, but I've run into a slight snag.
I'm gonna start the campaign off with the pen and paper RPG equivalent to an opening cinematic: an Ordo Xenos Inquisitor, Tiberius, along with a few Deathwatch Space Marines, have been dispatched to investigate a possible alien artefact-worshipping cult on a Hive World. As they leave the space port one Deathwatch Space Marine, Alcaeus, is sent to scout, and Tiberius' party is ambushed well-equipped and well-informed cultists, leaving Tiberius wounded and all his accompanying Deathwatch dead. Alcaeus returns in a cascade of bolter fire and krak grenades, rescuing Tiberius by dragging him into the nearest building, a barracks.
The PCs are in the barracks, and will now by Inquisitorial Edict be conscripted into the Inquisition. The players are then going to have try to get the wounded Inquisitor to safety with the help from Alcaeus
Here they're sent by the Inquisitor to find out what they can about the cult. A small fight and interrogation of surviving cultists. Alcaeus and Tiberius stay away as to not arouse suspicion.
Showdown with the cultists, only to find out the artefact they're worshipping was brought by a red-armoured Space Marine calling himself the Bearer of the Word. They learn he's not on the planet anymore, but find out that the ship he left on went to a Feral Planet inhabited by techno-barbarians.
Pursue the Word Bearer to the Feral World and have some Mad Max-style fun tracking him down.
Plot Twist #1: It was the
a) Alpha Legion
b) Ghosts of a Eris, a homebrew Alpha Legion successor chapter masquerading as loyalists
who let the Inquisition know about the cult. Plot Twist #2: The surviving Deathwatch Space Marine is infiltrating the Inquisition and planned the ambush in an attempt to build trust between him and the Inquisitor. He is actually
a) an Alpha Legionnaire who has literally transplanted the previous marine's face onto his own or b) a Ghost of Eris who has literally transplanted the previous marine's face onto his own.
The Alpha Legion/Ghosts of Eris are infiltrating the Inquisition to try to turn Tiberius into a Hydra operative (Potentially with psycho-indoctrination), or if that fails, to replace him with an Alpha Legionnaire/Ghost of Eris.
Plot Twist #3:
Unbeknownst to everyone, the Alpha Legion/Ghosts of Eris are actually rooting out the Word Bearer cult due to
a) they don't want the planet to fall to the Word Bearers
or if Alpha Legion
b) they want to take over the cult
c) the cult is in direct competition with one of their own cults
or if Ghosts of Eris
d) they want an uncorrupted planet to recruit from, so to arouse the least amount of suspicion.
Alcaeus also has special Alpha Legion equipment - specifically disguise equipment to allow himself to appear as a normal human. This equipment was used by Efritt squads previously (see the Primarch short stories).
In summary, the PCs will be doing the Alpha Legion's dirty work. If they eventually learn they're being duped it might be too late for them and they'll already be branded heretics, or it might be early enough to foil the Alpha Legion/Ghosts of Eris' plans, and maybe even expose them, or at the very least prove their own innocence (not that it'll count for much). Hell, they might even join the Alpha Legion or Ghosts of Eris to potentially become Space Marines, or convince Tiberius that the only way out is Exterminatus. Potential ideas: The alien artefact is a necron artefact (this has been done to death though).
The alien artefact is an Eldar artefact.
The alient artefact is a Chaos artefact.
The Feral World harbours many dark Chaos beasts (Mad Max, meet Riddick).
The Alpha Legion/Ghosts of Eris try psycho-indoctrinating the PCs.
The snag is I'd rather have them work with the Ordo Hereticus, but that blows the Deathwatch out of the plot. Any ideas how to circumvent that and what sounds more fun, the Alpha Legion or the Ghosts of Eris? Also, any thoughts or potential ideas?