Since I have volunteered to be Beta SG, I keep trying to think of storylines I can run. I have half an idea that I would appreciate people critiquing.
Our troupe has based itself in the remains of the rediscovered London Covenant, and quite a few of our grogs come from the north of London, acquired when we went looking for an old Vis source at Seven Sisters where the first 7 walnuts that drop each year contain a pawn of Vis. The primary SG points to Wikipedia which says "...name is derived from seven elms which were planted in a circle with a walnut tree at their centre on an area of common land known as Page Green".
My idea is that this is a Faerie Aura, and the elms are home to 7 Faerie sisters, and that recently an itinerant preacher recently gave an impassioned sermon there, where he symbolically placed the congregation's 7 Deadly sins in each of the elm trees. The faerie sisters have had their stories modified so that each of them now play act one of the deadly sins (Sloth, Lust, Gluttony, etc).
Since the change of story was caused by a faithful preacher, a Divine create, probably a wolf, shows up to corral the enthusiastic faeries. And naturally an Infernal creature will show up to counter this.
Our troupe has a Merinita magus, a character with a Guardian Angel, a character Infernally tainted, and a couple of characters with a Weakness for Women.
Not having access to RoP:Faerie, I don't know how bunkum this idea is.
Also, I am not clear on what the end-game would be. Thinking about it, our Flambeau might just burn the grove down, not caring it is a Vis source.
A key idea in RoP:Faerie that might help you get the "end game" is Vitality. Faeries plot and act to steal Vitality from humans. Each faerie steals vitality in a different way, e.g. the faerie of Lust might gain vitality by causing men to sleep with her, the faerie of Gluttony might seep away the will-power of people she seduces into gluttony, and so on. This can be more subtle or supernatural, for example the faerie of Sloth could benefit from people giving it their time, which means that they find that they are constantly pressed for time since they bargained it away - think modern-day people, that find they're constantly busy and stressed. A key point here is that, generally speaking, people should willingly give their Vitality away in some manner, symbolically. Faeries don't steal vitality, the mortals must give it to them.
You could have the sisters newly-energized by the new stories being told about them, and thus manifesting and appearing and plotting to gain more Vitality in these new ways, which they haven't done before.
Now, a risk here is that since this involves the Seven Sins this runs very, very close to being Infernal in nature. I'd suggest a possible course of action would be for a demon to seek to Corrupt the Seven Sisters, using this opportunity to bring them over to the Infernal Realm, turning them into demons rather than Faeries. You could make the key point here being convincing them to steal Vitality rather than bargain for it - to take it from humans, by force, rather than convince the humans to give it to them.
The Divine agent, in the meantime, should seek to transform the stories into something more benign. Having each Sister be a guardian against the sin rather than promoting it, say. Or it may seek to abolish the pagan practices entirely, or replace them with proper supplications for Christian saints, or whatever.
Well, I don't know if any of that helps, but it sounds like a nice setting. I hope you have fun with it.
I will also note that ROP:F has NO rules for gaining an losing Vitality. It states something along the line of: This is a storytelling telling tool. If a Fairy is having actions that reinforce its story it is gaining vitality. If it is not gaining those actions it is not gaining vitality and will either leave, force the issue, or change its role.
The sisters could then be both the tempters AND the reminders it's a sin. One sister does subtle lust, while another approaches the man at night on the way through the forest putting the fear of god in him... literally.