Clockwork Swarm | Magic: The Gathering
Formats Clockwork Swarm is Legal in
Official Oracle Text for Clockwork Swarm
Clockwork Swarm can't be blocked by Walls.
At end of combat, if Clockwork Swarm attacked or blocked this combat, remove a +1/+0 counter from it.
, : Put up to X +1/+0 counters on Clockwork Swarm. This ability can't cause the total number of +1/+0 counters on Clockwork Swarm to be greater than four. Activate this ability only during your upkeep.
Official Rulings for Clockwork Swarm
10/4/2004 : Can attack or block even if it has no counters.
10/4/2004 : If the ability to add counters resolves when there are already the maximum number of counters on it, any counters over the maximum are simply not added.