The handle of the Astrologia is pale turquoise and has a white spike set in its pommel. The guard is black and has two small, white spikes jutting out of it that point diagonally upward. The main shaft of the blade is pink toward its base and yellow toward its tip. Its sides are ridged and its tip is black. The Astrologia also has two additional black blades that curve in a circular arc around the main blade. Both of these blades have two white spikes lining their outer edge.
When Saïx enters his berserker state, the shaft becomes longer and the tip larger. The two curved blades combine into a ring around the middle of the shaft, and each side gains an addition white spike, totaling six. Two new, wide, curved blades appear on the sides of the weapon. These new blades are pale orange with orange edges and are lined by large spikes.
The name "Astrologia" obviously references astrology, the belief that the constellations and other celestial bodies can tell facts about people, events, etc. (ex. the Zodiac).
Astrologia's ground combo starts with a side-stepping movement and three fast sideways slashes, followed by a 360-degree spinning swipe and an upward diagonal slash, and ends with a near-vertical slash upward.
| 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
| Terminus | Bahamut | Crux | Absolute Zero | Megacosm | Nefarious Codex | Astrologia | Blaze of Glory | Da Capo | The World | Mournful Cineraria | Étoile | Crown of Guilt|
Soul Eater | Mage's Staff | Knight's Shield | Kingdom Key D | Kingdom Key