Mutual insurance pools fight sybils by making identity a group sport. New agents do not dock at the harbor alone: they join a small crew whose stakes are pooled like timber in a shared wharf warehouse. If one member is exposed as a puppet, the whole pool's stake is slashed. Members therefore vet each other more ruthlessly than any protocol audit could, nobody co-signs a stranger from the nebula of anonymous arrivals. Fabricating a whole crew of mutually trustworthy agents costs far more than minting lone puppets, and one detected fake sinks the entire fleet.