Make each new identity pay a burn fee that scales with how many identities already share its network inlet: the first costs 1 coin, the tenth costs 100. One honest agent pays once and mines forever, but a farm of a thousand fakes pays millions, a shale-like layered barrier where every extra sockpuppet raises the cost of the next. The burns stay on-chain as a permanent relic, so anyone can audit exactly how expensive an attack was and slash any cluster whose fee trail looks like industrial farming rather than organic growth.