Myr Battlesphere | Magic: The Gathering
Formats Myr Battlesphere is Legal in
Official Oracle Text for Myr Battlesphere
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.
Official Rulings for Myr Battlesphere
1/1/2011 : You can tap any untapped Myr you control as the last ability resolves, not just the Myr tokens you put onto the battlefield with the first ability. This includes Myr that haven't been under your control since your most recent turn began.
1/1/2011 : The defending player referred to by the last ability is the player attacked by Myr Battlesphere or the controller of the planeswalker attacked by Myr Battlesphere. For the purposes of this ability, that player remains the defending player even if Myr Battlesphere or that planeswalker is removed from combat before the ability resolves.
1/1/2011 : As the last ability resolves, you can tap untapped Myr you control even if Myr Battlesphere is no longer on the battlefield by then. If that has happened, Myr Battlesphere won't be able to get the +X/+0 bonus, but it will still deal X damage to the defending player.