Cagliostro was the author of a mystical grimoire known as the Book of Cagliostro.
Cagliostro came in contact with the Mystic Arts. He was able to study the Eye of Agamotto, learning the spells and gestures necessary to properly use it, as well as the power the relic could exact on the time continuum. He also learned the secrets and dangers of the Dark Dimension and its ruler, Dormammu.
Cagliostro eventually recorded his knowledge in a grimoire that eventually came into the possession of the Masters of the Mystic Arts and held in the library of Kamar-Taj as part of the Ancient One's private collection.
- Historically, Count Alessandro of Cagliostro was the alias of Giuseppe Balsamo, an 18th Century Sicilian alchemist. In the comics, Cagliostro was one of many aliases adopted through history by a sorcerer who achieved immortality thanks to knowledge of the Darkhold. He was a teacher of Victor von Doom and an enemy of Doctor Strange.
- Cagliostro was also an alias used by a different character, the time travelling sorcerer Sise-Neg.