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 the gestures necessary to properly use it, as well as the power of the relic over the time continuum. He also learned the secrets and the dangers of the Dark Dimension and its ruler, Dormammu. Cagliostro eventually wrote down his knowledge on a book, that was collected by the Masters of the Mystic Arts and held in the library of Kamar-Taj as a part of the Ancient One's private collection.
- Historically, Count Alessandro of Cagliostro was the alias of Giuseppe Balsamo, an Italian alchemist. In the comics, Cagliostro was one of the many aliases through history of a sorcerer who achieved immortality with the 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.