The Lunatic is a Claymore that can be wielded by Saïx in Kingdom Hearts 358/2 Days. In Kingdom Hearts II and Kingdom Hearts III, the Lunatic is his only weapon. In Kingdom Hearts III, Xion also uses a Lunatic while copying Saïx's berserker state.
The Lunatic has a smooth, white handle with a grey spike set in its pommel. The guard is a pale yellow semi-circle with four small notches in its outer edge. The lower part of the main blade is thick and has concave sides, each side being lined by three small notches. The blade is pale blue and has blue-grey edges. The lower half of the blade is decorated by two small, light blue diamonds. The tip of the Lunatic is a blue ring with dark-blue edges and lined by seven spikes. The tip is connected to the main blade by a pale yellow symbol shaped like the top half of the Nobody logo.
When Saïx enters his berserker state, the tip of the Lunatic is divided into two large, identical halves, each with three complete spikes lining the outer edge. These halves also gain four enormous, pale blue spikes shaped like those on the Nobody logo. The two halves retain the coloration of the normal Lunatic and are connected to the main blade by the cross-shaped symbol, which has become slightly larger.
The word "lunatic" comes from the belief that the moon induces madness, much like Saïx's Berserker state is entered with the moon's power.
Lunatic's normal ground combo consists of two identical, fast downward diagonal slashes followed by a leap forward and a more powerful downward diagonal slash. The -Combo can be activated after the second attack, and consists of a dash forward, followed by a 360° spinning swipe.
The aerial combo consists of a sideways slash, followed by an upward diagonal slash and a more powerful downward vertical slash.