The Gibbous has a short, black handle with a white spike set in its pommel. Its guard is gold with blue-grey edges on its underside. Its tips are bent downward nearly at right angles. The blade is wide and each side sports two elegant, curved spikes that point downward. There is a thin, oval-shaped gap in the middle of the blade and a thin split running up the center of the upper half of the Gibbous's blade. The whole blade is sky blue with blue-grey edges.
When Saïx enters his berserker state, the shape of the Gibbous's blade changes drastically. The spikes lining the weapon's sides lengthen and become larger. The upper pair of spikes now point straight up and curve inward slightly. The lower pair now points nearly horizontally and curves upward slightly. The oval shaped gap in the center become longer, thinner, and becomes a lens shape. Additional, wide blades are now present on the tips of the lower set of spikes and a lining the upper half of the blade. These new blades are white with sky blue edges.
The Gibbous moon phase occurs when roughly three-quarters of the moon is visible in the sky.
Gibbous's ground combo starts with three consecutive, near-vertical slashes upward, followed by a leap and a 360° spinning attack, and ends with a downward vertical slash.
The aerial combo consists of a dash forward in mid-air and a 360° spinning swipe, then a fast sideways slash, followed by an upward diagonal slash and a powerful downward vertical slash.