Aleister Crowley appears in the anime Undead Murder Farce as a self-proclaimed researcher of magic and numerology. He is a supporting character who becomes involved in the central conflict surrounding a precious gem known as the Penultimate Night. Crowley belongs to a group that comes into possession of a crucial item that drives the story forward: the stolen body of the immortal detective Aya Rindo. His awareness of this fact is demonstrated during a conversation where he notices Aya’s disembodied head in a birdcage and contemplatively informs her that his associates might have the rest of her.

In terms of combat abilities, Crowley employs a distinctive fighting style that uses various needles to simulate magical attacks. This technique allows him to engage effectively even against formidable opponents, as seen when he forces the legendary detective Sherlock Holmes and his partner Dr. Watson to exhaust all of their ammunition. Crowley also makes use of poisoned needles as part of his arsenal, attempting to use one against Holmes during their confrontation. His fighting approach, much like his conversation style, is characterized by cunning and indirection; interactions with him feel like fencing matches where opponents are constantly trying to outmaneuver one another.

Crowley is part of a larger group that includes the vampire Carmilla, with whom he is shown confronting the combat maid Shizuku over the location of the werewolf diamond. His role in the narrative places him in direct opposition to the main characters, including Aya, Tsugaru Shunichi, and their allies. He appears in multiple episodes of the series, including the episodes titled The Immortal of London, Free for All, The Banquet, and The Culprit's Name. Throughout these appearances, he is portrayed as a calculating individual whose actions are driven by his interest in magic and the supernatural forces that shape the world of the story.