The Book of Shadows, as legend has it, was penned by Gethzerion. This book was the core spiritual text for the Nightsisters' society on Dathomir.
Mother Gethzerion, upon establishing the Nightsisters of Dathomir, informed her followers that the original Witches of Dathomir's moral compass, the Book of Law, was produced after Allya had grown frail and elderly. Gethzerion then initiated her own instructional text, titled the Book of Shadows, to supersede it. This volume detailed the spells and rituals she devised specifically for the Nightsisters.
During the era of the Clone Wars, Talzin, a Shaman of the Nightsisters, asserted that the Book of Shadows was actually a recovered version of Allya's authentic teachings. She claimed Allya's writings lacked the concepts of "good" and "evil", and the Book of Law was a fraudulent work crafted by Sisters who had been "weakened by the Jedi blood in their veins".
- Cracken's Threat Dossier (First mentioned)
- The Dark Side Sourcebook
- Jedi Academy Training Manual
- " Everything You Always Wanted to Know about the Nightsisters but Were Afraid to Ask " — Star Wars Insider 122 (also reprinted in Special Edition 2014)
- Book of Sith: Secrets from the Dark Side