The coffin. The corpse that was not.

When circulating iron falls below a critical threshold the Archon initiates a controlled shutdown. Neuroinhibitory compounds hit the brainstem in sequence: peripheral vasoconstriction first; then suppression of sinoatrial pacemaker cells, dropping an already low resting rate of twenty to thirty beats per minute to one or two — a pulse that cannot be palpated and needs electronics to prove; then medullary respiratory arrest; then core temperature collapsing to ambient as bio-voltaic heat output falls to effectively zero.

To any examination technology available before the late twentieth century the host is a corpse. No pulse. No breath. No heat. No pain response: ascending pathways from periphery to thalamus have been switched off. The colony keeps the minimum required to preserve cellular integrity and its own viability. Folklore put this body in a box because a box is what you do with a corpse. The organism was waiting for iron.