Maybe Something had a Rampire imprisoned in the NN or some other place with defenses powerful enough to block the bloodline curse, and now said Rampire is being imprisoned and tortured and milked like livestock? It would be an interesting twist for the "innocent" that needs rescuing to be a Rampire...
That's another evil thought!
You folks are geniuses.
(I note that "defenses" wouldn't AFAIK stop a bloodline curse -- at various times iirc Harry has been pretty clear that, magically speaking, "blood" bypasses pretty much any/all defenses. Being in the Nevernever
might do it (for your game, if you'd like some Rampires to surprise your players this seems like an excellent rationale!).).
Upon consideration:
1. Where do RCV's come from? What's the origin of the 1st-ever RCV? Might there be a hidden reserve or pool of them (e.g. living natively in the Nevernever)?
2. Maybe Lea wasn't the only one wearing a mask of one of the Lords of Outer Night: maybe one of the LoON's scarpered off to the Nevernever when Fidelacchius made a showing (because you've
gotta know that when a Knight shows up with a Sword
and then an angel speaks through their voice, there's just a WORLD o' hurt about to come down on the Bad Guys!), leaving a lieutenant to fight and die in their place.
3. IF the Nevernever is a sufficient protection from the bloodline curse... it would actually be kind of surprising (given all the thousands of RCVs & RCI's running around) if there weren't SEVERAL of these (accidentally or deliberately) NN-protected RCVs.
3a. If the bloodline curse has destroyed all the mortal-world RCVs
and the connection between them, then Rampires coming out of the NN are now disconnected, and no single Bloodline curse can take them all down, anymore...