A vampire seduces a powerful alchemist, with the intention of getting her to craft a powerful item (maybe a +20 rapier) the alchemist, deeply in love with the vampire, cant ignore what he really is and betrays him by trapping him in the pommel of the sword. She still has her love, but the blood flow stops. Destroying the pommel, that would require a powerful alchemist again to dismantle would rid the curse and the pc keeps the sword. If the pc attempts to destroy the pommel it could release the vampiric spirit.