I'm a little unclear about this; maybe it was addressed somewhere and I'm just not seeing it, given how busy I've been lately. But, who precisely can do this, and is there any game mechanical effect?

To give you some context for my question, one of my PCs, a member of the Adeptus Sororitas, is about to be excommunicated entirely on the false testimony of a traitor within the Inquisition itself! The other PCs are convinced of not only her innocence, but of the rival Inquisitor's guilt (she's been collaborating with heretics of Chaos), so things are about to get very interesting. What I need to know is could Excommunication itself bar a Sister of Battle from using her Faith Talents, even though she's utterly innocent?

Wayfinder said:

To your very last question, I'd say that is outside the dominions of an excommunication entirely (except for possibly what it might due to the sister and thus her beliefs). As long as the individual themselves is really and honestly true to the strait and narrow and believes that they are, their Faith will stay with them no matter what politics happen around them.

That was my thought as well. Surely the Emperor knows her heart, on some level, was the way I thought about this, and I was getting set to make a ruling along those lines. However, I wasn't too sure.

Another question arises when she might do something to break her oaths to the Sisterhood. Not that she has done it, but there are times when this Sister of Battle PC seems a bit friendly toward the Guardsman PC who has repeatedly saved her life (He and the party Psyker ran into a Chaos Cult's stronghold to save her from being sacrificed - and came to love Heavy Bolters). So far, there's been nothing romantic between the two, but I have to prepare myself for such an eventuality.

Wayfinder said:

And? Just roll with it. Nothing about Pure Faith stops any fraternising with a fellow party member.

Honestly, until you get to Ascension and all the Influence-cutting that Excommunication would involve (which is honestly beyond the scope of what I can answer for), I'd just cut any Peer talents she might have with the Sororitas, ecclesiarchy, and any notable allies (administratum, imperial guard?) depending just how "public" the exile is. Perhaps even gain a Rival or Enemy trait, again, depending on just how severe and public this exile would be.

There's nothing stopping the character from acting in a manner which would denote the loss of Pure Faith through acting out of shame, guilt, petty revenge or frustration upon exile (depending on the player's interpretation of his/her character), but out and out losing it seems unfair to me. It kinda smacks of railroading to me, in a sense.

I would agree with what people here have said thus far. Pure Faith is not about your place in the imperium, it's about your personal connection to the god emperor. Being excommunicated unjustly, having a romantic relationship that is technically frowned upon, etc, would not affect that.

For support, I'd point out the background package for outcast sisters in the Radical's Handbook, who keep all their pure faith talents.

Firstly, the Sister most likely gets to keep her Faith unless she believes herself to be tainted (in which case she probably won't be able to access it on a psychosomatic level) or flat-out becomes tainted .

Secondly, the greater problem with Excommunication is that it tends not to cut a few peer talents, but make you a Persona Non Grata virtually everywhere it's known and paint a nice big bullseye on your head for every hard-liner in the sector. If her order believes the Inquisitor, they'll likely be among the first ones to hunt her down to spare the order the disgrace of an apostate.

And finally, it's not exactly clear whether Sororitas have to be celibate. While they are officially wed to the Emperor, there's nothing saying that this "wedding" has to mirror the present-day catholic one, with physical faithfulness thrown into the deal. A while ago, there was quite an interesting thread about how planets could have different customs regarding sexuality and marriage. I'd generally assume that most Sororitas orders have their own rule, which may or may not specifiy celibacy - the Celestian from Cain's Last Stand definitely hasn't made such a vow and neither do the novices seem to.

For the celibacy bit, it depends how strongly a particular Sister takes her vow as being "wedded" to the Emperor. If they take it literally, then they will often be celibate. If they take it as a more figurative vow, then there would be nothing stopping them from not being celibate. It's all down to the particular Order the Sister is part of, basically.