Spirits of the Shadow Realm is a book which exists in the 2017 Continuum.
This old tome written in Ancient Syriac contains information on various kinds of spirits to be found in the Shadow Realm, with stylized illustrations. This includes Tulpas, psychic manifestations of strong emotions. A copy of Spirits of the Shadow Realm is among the many occult books to be found at the Duckburg Public Library.
In 2019, Webby Vanderquack and Violet Sabrewing both tried to check it out at the same time, Webby as part of her ongoing project to find a way to free Lena De Spell from the Shadow Realm, and Violet as part of her intensive research into the paranormal which had been sparked by the Shadow War.