So somewhat expectantly, I guess, Oriana was both a decoy and a pawn, used to throw the scent completely off of St. Peter’s Cross while in a way being duped into helping Lidvia who, sadly, sounds too much like today’s religious fanatics, trying to use the cross as a way to make science subservient to religion once and for all by claiming control over Academy City. In the end, she was foiled by the Night Parade’s fireworks, and then sucked out of a plane by Archbishop Laura who was rather ruthless in her dealing with Lidvia.
I thought this arc ended rather lamely. Oriana was finally done in by a punch, of all things (after she had already taken several) and Lidvia was foiled no thanks to all the events in the past six episodes in this arc. I mean, it was a somewhat exciting arc, I guess, but I felt kinda cheated that the last 6 episodes led to a conclusion where nothing they did actually stopped the threat.
As for Archbishop Laura, I’ve always kind of found her a creepy kind of sweet, and she showed it here when she just dropped Lidvia from the plane (along with the pilot), presumably destroying the cross along the way (though I think that part might be in dispute). Lidvia seemed to be rather crazy, anyway, and rather obsessed with making the Roman Catholics dominant by “denying science” as she put it (not that that’s very different from reality, though the Catholic Church is hardly alone in that regard).
So at the end of this arc, everyone is all happy again. The main thing that last might be that Himegami may be more involved in the romantic feelings for Touma now. Of course, this changes things from merely being an Index-Touma-Mikoto triangle to an full on harem for Touma. Luckily there don’t seem to be any other females that would seem to imminently become romantically interested in him at this point.