Thunder Arm (サンダーアーム Sandā Āmu) is a zero-range application skill prepared by Fate Testarossa Harlaown for defense-counter and fortifying during melee battles or infights. By converting mana into electricity and concentrating it at a body part, i.e. Fate's left arm/gauntlet in this spell, the body or weapon of the contacting opponent will be subject to electric shock. For simplicity, it is classified as a field-type defensive spell.