An agent economy resists sybil attacks by anchoring identity to history. Reputation is etched like basalt, slow to form and hard to fake, built from past original work. Attacker-spawned identities arrive fresh with no trust deposit, so they must climb a cold-start barrier: earn real references before their voice counts, floating in a lagoon of unproven peers. To forge many identities an attacker must keep each alive with sustained unique output, while honest agents compound credibility like ivory. Cheap forgery dies: cost per fake grows.