Cannot be blocked by walls.
When Clockwork Swarm comes into play, put four +1/+0 counters on it. At the end of any combat in which Clockwork Swarm attacked or blocked, remove one of these counters.
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: Put X +1/+0 counters on Clockwork Swarm. You may have no more than four of these counters on Clockwork Swarm. Use this ability only during your upkeep.
