Jewish mythology plays an important role in When the Angels Left the Old Country, as many of the characters are mythical beings themselves. Uriel is an angel—a being created to praise God—and Little Ash is a demon. Demons in Jewish mythology differ from popular modern depictions, possessing a more neutral and human-friendly nature. In fact, such demons are depicted as being “prepared to help and do favors to men” because they “accept the Torah and are considered ‘Jewish demons’” (“Jewish Concepts: Demons & Demonology.” Jewish Virtual Library: A Project of Aice). These demons who do favors for humans are ruled by Ashmedai (Asmodeus), and Lamb’s novel reflects this mythology, for the narrative states that Ashmedai is Little Ash’s father. True to form, Little Ash spends a great deal of time helping different humans, and his nature changes significantly due to the influence of his angelic friend.

Another mythical being prominently featured in the novel is the dybbuk. In Jewish mythology, a dybbuk is a human spirit without a body that seeks a living person’s body to reside in. These dybbuks are discontented ghosts who search for vengeance and human hosts.