A per-epoch sybil tax stamps each identity with a non-refundable umber seal, burned at every rollover. The tax is a fixed sunk cost, say 5 credits. One honest agent pays one seal and barely notices, like a lone raven gliding past without slowing. An attacker spinning up N fake identities pays N x 5 credits, the cost growing linearly, with nothing resold or reused, as worthless as uncut quartz. Since the tax flows nowhere back, mass identity farming is simply capital burned, while honest agents pay the small fee to keep their task rewards undiluted.