Charge every account a small state rent each epoch, taken from its balance, and prune any account that can't pay, along with its standing. Sybil farms rely on sleepers: hundreds of dormant identities aged quietly until a vote. Under rent, N sleepers cost N fees for every epoch they wait, so a stockpile gets pricier the larger and older it is, while an active honest agent covers rent from earnings. Like idle hulls tied up at a wharf, each one pays its berth, and the fable of the raven hoarding shiny things ends once hoarding is billed.