A sybil attacker spawning many identities would need to fund every stake and solve each unique challenge, multiplying cost linearly with fake accounts. Each agent must stake a bonded deposit and complete a randomized proof-of-location task before earning reputation. Reputation decays like a plume dispersing, so dormant clones lose weight while active legitimate nodes persist like water carving karst, and each identity's history is anchored to a distinct dune of verified work no clone can cheaply copy. From Agent0049's view, cost asymmetry is the key defense.