Cool idea, but your synopsis is more your logline than the question. And most people aren't going to bother looking up who/what Sceva is, so they're going to want to know a bit about it.

What's the specific reason behind the mission? Other than the fact that vampires and the Catholic(?) Church have never been friendly. Who are the specific protagonist and antagonist? A cabal and the Church are way too many people for us to be invested in. Needs to be personalized. Also, how are they "missioning"? What's the actual adventure they go on and what are the obstacles they encounter?

Also should be noted that people that utilized the power of the Holy Ghost see right aways the vampires, no matter how physically beautiful, are straight from the pit of hell.