Whenever a creature you control attacks, put a charge counter on Druids' Repository.
Remove a charge counter from Druids' Repository: Add one mana of any color.
5/1/2012 The first ability of Druids’ Repository will trigger once for each creature you control that attacks.
5/1/2012 You can activate the second ability of Druids’ Repository multiple times in the same turn. It’s a mana ability, doesn’t use the stack, and can’t be responded to.