The mage can destroy Mana.
One point of Mana, no matter how it is stored (as tass, within an artifact, or a mage’s own personal Mana points), may be destroyed per success.
Adamantine Arrow Rote: Plucking Teeth
A gun without ammunition is largely useless. While the same cannot be said of a mage without Mana, such a willworker is nevertheless cut off from many of her most powerful magics. Arrow mages enjoy using this rote against enemies that have become reliant on advanced magic.