Quote:
How and why is the vampire humane? A soul, or something else?

Why was the Seraph exiled? - Craig Oxbrow
Could these be connected? Perhaps the Seraph did something to the vampire to restore their "humane-ity," but which violated some non-intervention clause or other.

Or the process of exile went wrong and left trails of divine energy scattered across the city (something like the mass-infection that Illyria could have become): the energy has settled in various beings including the humane vampire Cast member; a fanatical messiah-vampire (or human, or even a pairing, which might alert the cast as to the oddness of situation); several humans now possessed of supernatural gifts, but with a tendency to combust without warning in a flash of angel-fire; several demons partially transformed, with mystical gifts, one believing (rightly or wrongly) that it can now storm the powers' own gates. When one of these recipients is killed, the energy drifts around until it finds another host. Let the Cast deal with cleanup until they can find some way to dissipate the energies altogether. Let them sweat on whether they can do this without reverting their vampire to evil.