Ireth
Myth Weaver
This is an issue that comes up near the end of my vampire novel. A vampire character sacrifices himself out of love for another, and comes back to life as a human once his death is avenged by another character killing the one who killed him. The "escape clause" is not mentioned at all in the beginning of the novel, even by the Goddess herself when She appears to the hero (or any other vampire for that matter), for a very specific reason: because of the nature of sacrifice, any vampire who knows about the clause beforehand might actively seek his own death in order to be restored to humanity, and the self-seeking would negate the sacrifice. As a consequence of this, any vampire who turns human loses all memory of the surrounding circumstances so s/he can't tell others about it, and any witnesses are left in the dark as well. The possibility of such an escape clause is alluded to, but none of the vampires know what it is, with the reasoning that "if I knew what it was and could fulfill it, do you think I'd still be like this?"
My main trouble with this is keeping the nature of the escape clause just as it is, and keeping it hidden from the POV character (and thus the audience) without making it seem like an ass-pull to keep my beloved character from being killed off for real. There's literally no vampire who could possibly tell anyone else about the sacrifice clause, so even hearing about it second-hand wouldn't work (and it would defeat the purpose anyway).
My main trouble with this is keeping the nature of the escape clause just as it is, and keeping it hidden from the POV character (and thus the audience) without making it seem like an ass-pull to keep my beloved character from being killed off for real. There's literally no vampire who could possibly tell anyone else about the sacrifice clause, so even hearing about it second-hand wouldn't work (and it would defeat the purpose anyway).