 In a letter to Clark Ashton Smith, Lovecraft proposes that Warren may have been destroyed by a "begetting entity" in Smith's tale "The Nameless Offspring".A character who bears a resemblance to Warren is Clark Ashton Smith's antehuman sorcerer Haon-Dor (from "The Seven Geases"), another seeker after forbidden lore.Warren is also mentioned in Brian Lumley's "Titus Crow" series as a member of a Bostonian group of psychics.