So in the Only War Core Rulebook, there is a small blurb about the Dark Heresy supplement the Apostasy Gambit. For those of you not in the know, it deals with an impostor posing as the return of Saint Drusus, and how this fractures the Calixis Sector into factions who either believe or disbelieve the "returned" Saint. Duke Severus XIII is one of the non believers, and rightly calls him out as a fake from the start. The Rulebook goes on to state that for a GM, this would be an interesting campaign setting, particularly for a group of players who may have been promoted to command positions. Which side do they take? How far will their devotion to the "Saint" go?

I think this is an excellent idea, and while I don't personally own the Apostasy Gambit trilogy, I would love to try it. Has anyone done it before? How did it go? If you haven't tried it, would you?

I haven't tried incorporating it into a non DH game yet. But it's something I've thought about for a while, specifically in my RT game. I'm not sure if I want to play it off as a background event, seriously reconstruct the books for a RT game, or just use it for fodder for an entirely new story. It's definitely something I want to get to. I should probably go read the books myself to see how cool and suitable it is.

How would I do it with OW? You can have it be background. Your regiment says he's real, and is gonna trounce these traitors partly in his name. Then it comes out, that well, he was sorta a fake, and high command plays it off as a ruse by the Dominate. Maybe you have it lead to a civil war between loyalists forces on an otherwise kinda quiet planet. The whole game is about fighting the regiments who disagree with you. Or maybe it's a mania and witch hunt that slowly creeps through your own regiment, causing intense fractures in between scenes of your fighting orks that slowly comes to a head. Platoon style(great movie with a lot of applicability to OW I'd say)!

Of course one way to sorta reference it in a meaningful way, without really going at it is. Have your guys be aware of it, and hearing rumors about it. But be mostly uninterested. Most PC regiments aren't from the Calixis sector. Drusus is just another saint out of millions, he sounds cool, but he's not your favorite messianic figure from childhood. The locals getting worked up into a murderous froth over it is sorta unsettling. And reminds you of just how far you are from a home you're likely to never see again. You're on a strange planet, surrounded by strange people. Even the ones who are on your side barely share the same language or the same god. They fight, pray, talk, dress, look, smell, and eat different among other things. They're killing each other over some resurrected saint, when there's chaos cultists creeping into their trenches. Honestly the whole thing is unseemly how they venerate the saint, they almost treat him as well as the God Emperor, it's borderline blasphemous honestly.

From what I've gathered about the background of the event, it had massive ramifications for the entire Calixis Sector. While it could be played as a minor insurrection, imagine the impact it would have on the Spinward Front if the Dei-Phage's supporters began to fight the Imperial Guard and the Severan Dominate. With the players caught in the middle, it would provide a new enemy to face in the form of their former friends.

Following that vein, what if defeating the traitors meant the PCs teaming up with the Severan Dominate forces they had previously been fighting? After all, the enemy of my enemy is my friend...

Oh it is a massive event. I just meant that from the PCs' point of view, it could mean anything from a full scale redeployment, and a total shift in the campaign, to rumors they hear while they're fighting chaos cultists room to room on some planet removed from the fray.

What you said is definitely one way to play it. Either with them officially working together under a ceasefire, or them having a gentlemen's agreement to basically ignore each other. Though a big three way fight between the various regiments is another way to play it out.

No matter which way you go, you just have to keep in mind how to present this information in a compelling way to characters operating on the squad level. They're not going to be the ones redeploying everyone, or setting up any new treaties. But they will get briefings, receive rumor and propaganda. They will have decisions to make in the field. They see one convoy of rebels driving into the killzone of another's ambush. What do they do if anything? That sort of stuff has tons of angles.