Defender : Add X mana in any combination of colors to your mana pool, where X is the number of creatures with defender you control.
Only a worthy few are permitted within the sentient forest known as Axebane.
Official Rulings for Axebane Guardian
10/1/2012 : Axebane Guardian's activated ability is a mana ability. It doesn't use the stack and can't be responded to. The number of creatures with defender you control is counted, and the color(s) of mana produced chosen, immediately after the ability is activated when the ability resolves.