The Astrology Book is a book obtained during the Observatory Quest. Its contents tell a detailed story explaining the origin and character of the roaming ghost whom the player character encounters, the Spirit of Scorpius.
The Astrology Book tells the story of Scorpius, who was a well educated man known for his visions and skills in magic. Seeking to communicate with the gods of the world, he studied for many years and developed a magical machine. This machine was essentially a telescope which could see into the heavens and realms of the gods. Scorpius mapped the stars for many years, using his findings to "gain dark knowledge" and predict the future. After he died, the blueprints for his magic telescope were found at a Zamorakian site of worship. The book also details how the legends of his ghost roaming the area persist to this day, and that he will grant a blessing of power to those whom are worthy.