|"Wow! That's some classy gear."|
–William admiring his sword in "Final Round."
|First appearance|| Final Round (original look)|
William Returns (XANA's darker version)
William generally fights by using the Zweihänder's unusual size to his advantage, as it is capable of slicing two monsters all at once with one swing; unlike Ulrich's sabers.
In the final episode, Final Round, William primarily uses the Zweihänder to deliver slow but powerful blows, defeating Creepers with a single hit. For defense, William is able to reflect lasers by at monsters using the sword.
Since being possessed by X.A.N.A., the Zweihänder gains the ability to charge up and then release energy in the form of silver waves, which are also rather slow to execute, but exceptionally strong nevertheless.
After being released from XANA's control one year ago,, the Zweihänder receives several upgrades from X.A.N.A. (which also includes the ability of super smoke) With William's increased physical strength, the sword is easier to handle, increasing his dexterity with the weapon. The Zweihänder is also heavily integrated with William's Super Smoke ability, and he is able to use the ability to make the sword vanish when not using it, or summon it directly to him if he is separated from it.
The Zweihänder is a massive sword, longer than William is tall. It has a wide, single-edged blade and a long, thin handle. The blade is silver in color and glows white when being used in combat, including while charging a wave attack. Apart from these general features, the Zweihänder goes through several appearance changes throughout the series.
While William is under X.A.N.A.'s control, the Zweihänder's handle changes from red to black, and black, root-like structures decorate the blade. There is also an Eye of X.A.N.A. near the sword's hilt. While on Earth as a spectre, the Zweihänder blade is a darker shape of grey, and the roots on the blade are red instead of black.
In Code Lyoko Evolution, the Zweihänder's appearance changes again. The handle is black with orange stripes, and there is an orange, circuit-like design on the blade. The sword is also noticeably smaller than it is in the original series.
- A Zweihänder is a traditional German sword used primarily during the early 16th century. The name translates into English as "two-hander", and like William's weapon, real-world Zweihänders are known for their exceptional size, and must be handled with both hands.
- The Zweihänder's design appears to be based on the Buster Sword from the Final Fantasy series.
- The Zweihänder was the weapon that succeeded in destroying the Core of Lyoko, and thus all of Lyoko, in the season three finale.
- If one of Aelita's Energy Fields hits the Eye of X.A.N.A. on the Zweihänder, its blade will glow pink instead of white, and William will be able to redirect the attack in the form of a wave.