The blood exchange. Drinking from the sire.

Immediately after the Drain the host drinks Elder blood. The gastrointestinal mucosa dumps the load into portal circulation. The Elder has triggered viral reactivation: the sample is dense with HHDRV particles and HHDRV-carrying haematopoietic stem cells, acid-resistant, headed for marrow. Engraftment rewrites haematopoiesis over days to weeks. Red cells turn over fast, so the bio-voltaic shift begins within days. Neural rewrite takes months. Skeletal armour takes the five-year programme.

Archon larvae travel with that blood. In the peripheral phase they secrete a vasopressin analogue, an erythropoietin-like factor, and a platelet-activating compound — first responders buying time. Their cuticle mimics glycophorin A and Band 3, erythrocyte surface proteins, so innate surveillance reads them as self during the hours when adaptive immunity is at its nadir. They do not go to the brain through blood. They take the perineural route: olfactory nerve through the cribriform plate, and dorsal root ganglia into epidural space and cord, the same path Naegleria fowleri uses to bypass the blood-brain barrier. In the CNS they bias microglia from Th1 inflammation toward Th2 tolerance. Miss the window and the recovered immune system mounts a fatal encephalitis. The folklore of the blood exchange is a transplant protocol with a parasite as the anaesthetist.