Myr Battlesphere [Commander 2013]
Set: Commander 2013 Type: Artifact Creature Myr Construct Rarity: Rare Cost: null
When Myr Battlesphere enters the battlefield, put four 1/1 colorless Myr artifact creature tokens onto the battlefield.
Whenever Myr Battlesphere attacks, you may tap X untapped Myr you control. If you do, Myr Battlesphere gets +X/+0 until end of turn and deals X damage to defending player.