Donati's Horoscope had been the sole existing horoscope that had been discovered and retrieved by Academy City as a purely scientific item, making it a slight issue between the science side and the magic side. The Horoscope in question was a key item for the complete recovery of the Alaskan rune epitaph and the acquisition of its knowledge. The horoscope can be used to calculate the magical effects of Donati's Comet.