A bite is enough. One night and you wake changed.

A bite is never enough. Conversion is a transplant. The Elder first takes the prospective host to Class III–IV hypovolaemic shock: circulating volume down thirty to forty percent, roughly 1.5 to 2 litres in an adult. Blood pressure collapses. Peripheral beds are sacrificed to keep brain and heart. Adaptive immunity, riding on circulating lymphocytes, falls off a cliff. This is the same window trauma surgery and bone-marrow conditioning try to create: an immune landscape cleared so foreign tissue is not immediately killed.

The Drain is therefore two acts at once. It is immunosuppression without chemotherapy. It is also the creation of empty marrow niches — emergency haematopoiesis screaming for cells — so that what arrives next has somewhere to sit. Unsanctioned conversion is the gravest haemophagic offence because the window is lethal if mistimed and because a botched transplant produces a corpse, not a recruit.