The Maser Vibration Sword (MVS) (メーザーバイブレーションソード, Mēzābaiburēshonsōdo) is a type of weapon that uses a combination of extremely high oscillation rates and temperatures in order to increase the cutting effectiveness of the weapon, thus this leads to the gray material suddenly becoming red. Due to some Maser Vibration Swords having similar oscillation rates, they can collide with each other without being cut. It can be inferred that the deeper the color of red it is, that the MVS blade becomes the sharper, stronger, and more durable. Rakshata created a variant of the Maser Vibration Sword known as the Revolving Blade Sword.
The Lancelot was the first Knightmare seen using a Maser Vibration Sword. The Lancelot's MVS is stored in sheaths attached, by the cross-guard being folded, to the cockpit block. Guilford's Gloucester was fitted with a pair of MVS identical to the Lancelot's, stored in black scabbards on the sides of the Gloucester's cockpit. The Lancelot Club equipped a variant of the Lancelot's MVS that could be combined into a dual-bladed lance-type weapon. The same weapon was later equipped to the Vincent and its successors. The Tristan is equipped with two MVS Polearms, long-shafted and short-bladed weapons that combine to form a long, dual-headed spear. Also, the Guren S.E.I.T.E.N. Eight Elements has a smaller MVS version of the original Guren's Fork Knife.
The Galahad carries an enormous and extremely powerful Maser Vibration Sword, which was given to Bismarck Waldstein by Holy Britannian Emperor Charles zi Britannia himself and christened "Excalibur". It is far more powerful than most other weapons of this type, and its blade is a deep purple rather than red. The Excalibur is able to easily break through armor in a single swing, and is capable of generating an energy field that can block and slice through powerful energy blasts - a capability no other MVS weapon has demonstrated. After the Galahad's destruction, the broken Excalibur is reforged as two blades, which are equipped to the Tristan Divider.