As long as you control Pennon Blade, its ability constantly counts the number of creatures you control. It doesn't matter who controls the creature it's equipping (in case an opponent somehow manages to take control of that creature). If you control the creature it's equipping, the bonus will include that creature too.
Equipped creature gets +1/+1 for each creature you control.
Equip (: Attach to target creature you control. Equip only as a sorcery.)
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