The King of the Night is a fairly long Claymore with a short, yellow handle with a sea green spike set in its pommel. The shaft of the blade is predominantly grey with ridged, concave edges. There is a small, vaguely arrowhead-shaped section at the base of the blade that is dark blue in color. A thin, black border lines this blue section divides the shaft down the middle. The upper half of the blade is rather thin and forks into a "Y" shape at its tip. There is a long spike—reminiscent of those on the Nobody symbol—that slants diagonally downward connected to each of the two points on the tip. The whole upper half of the blade is dark blue and has thin, grey edges.
When Saïx enters his berserker state, the grey section of the shaft splits down the middle, along the black line present in the King of the Night's normal shape. The two halves are no longer directly connected to the weapon, and are instead attached to the handle and upper half of the blade by a new light blue section of the claymore that has thin, blue edges. The upper half of the blade becomes longer and wider. The spikes change shape slightly, with the lower half of each one now pointing outward sharply. The whole upper half is lined by a new, light blue blade with thin, blue edges. Fittingly, this Claymore and the Queen of the Night are virtually identical, differing only in color.
"King of the Night" refers to Saïx, the usurper of the night—it reflects Saïx's power of the moon.
King of the Night's ground combo consists of a forward dash and two slow 360-degree spinning slashes, followed by a leap forward and a powerful downward slash.
The aerial combo consists of a dash forward in mid-air and a 360-degree spinning swipe, then a fast sideways slash, and followed by an upward diagonal slash and a powerful downward vertical slash. This weapon has no -Combo.
| New Moon | Werewolf | Artemis | Luminary | Selene | Moonrise | Astrologia | Crater | Lunar Phase | Crescent | Gibbous | Berserker | Twilight|
Queen of the Night | Balsamic Moon | Orbit | Light Year | King of the Night | Moonset | Horoscope | Dichotomy | Lunatic | Just Desserts | Bunnymoon
| Annihilation | Energy Muzzle | Foxfire | Subzero | Hyperion | Lost Heterodoxy | King of the Night | Outbreak | Million Bucks | The Devil | Vindictive Thistle | Croix du Sud | Astral Blast|
Soul Eater+ | Mage's Staff+ | Knight's Shield+ | Kingdom Key D+ | Kingdom Key+