Artifact Creature - Myr Construct | Power/Toughness: 4 / 7 (CMC 7)
When Myr Battlesphere enters the battlefield, create four 1/1 colorless Myr artifact creature tokens.
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 the player or planeswalker it's attacking.
- [SOM] Scars of Mirrodin #180 (R)