Pentavus

Counters and tokens are the same resource here, just held in two different states. The five +1/+1 counters it enters with are not a body so much as fuel: each one can leave to mint a flying Pentavite, and each Pentavite can be sacrificed to return a counter, which means the card is a closed loop that converts between a single large threat and a swarm of small fliers at one mana per conversion. That fungibility is the whole engine. It feeds anything that wants tokens to throw away (sacrifice outlets, anthem-style attackers, blockers on demand) while also functioning as a mana sink that never runs dry, since the counters and tokens cycle back into each other indefinitely. The design lineage runs through earlier "counter as currency" creatures, but this is the version that built the storage and the spender into one card: the counters bank, the tokens spend, and the activated abilities are the teller window between them. Its vulnerability is the same as its strength. With zero base power and toughness, removing the last counter or killing the construct collapses the loop, so the player constantly decides how much of the engine to expose as a single consolidated target versus how much to spread across expendable bodies. That tension, between hardening into one large creature and dispersing into five fliers, is the running decision the engine generates turn after turn.