A cacodemon (or cacodaemon) is an evil spirit or (in the modern sense of the word) a demon. The opposite of a cacodemon is an agathodaemon or eudaemon, a good spirit or angel. The word cacodemon comes through Latin from the Ancient Greek κακοδαίμων kakodaimōn, meaning an "evil spirit", whereas daimon would be a neutral spirit in Greek. It is believed to be capable of shapeshifting.
In psychology, cacodemonia (or cacodemomania) is a form of insanity in which the patient believes that they are possessed by an evil spirit. The first known occurrence of the word cacodemon dates to 1593. In William Shakespeare's Richard III Act 1 Scene 3, Queen Margaret calls Richard a "cacodemon" for his foul deeds and manipulations. In John Fletcher's The Knight of Malta, Norandine calls Mountferrat, the play's villain, a "cacodemon" in the final scene. In The Arbatel de Magi Veterum written in 1575 the word Cacodemon is described as one of the Seven. In astrology, the 12th house was once called the Cacodemon for its association with evil.
In popular culture
- In the book and TV series The Magicians by Lev Grossman the main characters each have a Cacodemon magically implanted into their backs.
- Kelley Armstrong's Women of the Otherworld novels feature cacodemons and eudemons, some of whom have produced semi-human-like progeny; in this context eudemons are not so much "good" as "non-chaotic".
- Deicide's second album, Legion, contains a song called "Satan Spawn, the Caco-Daemon".
- There is a painting by Paul Klee called Cacodaemonic (1916).
- There is a boulder in Squamish, Canada called Cacodemon; it is the location of the climb Dreamcatcher, a 5.14d (9a) first climbed by Chris Sharma.
- There's a Cacodemon in the sewers of Wormy's lair in the Wormy comics for Dragon Magazine (124) by David Trampier. It is never shown, but when Grumble and Snaggly escape from Boon and Irvin in the sewers with half the payroll, Irvin says to Boon to lock the grate back as the treasure now belongs to the Cacodemon that lives in the sewers, the reason why Wormy kept it locked up. https://en.wikipedia.org/wiki/David_A._Trampier
- In the first edition of Advanced Dungeons & Dragons, "Cacodemon" is a seventh level magic-user spell. It was used to summon a type IV, V, or VI demon to the player character's location in the game world. The spell was omitted from the early versions of the second edition of the game, and was later revised in the Planescape product line, in which it could summon a variety of powerful tanar'ri or baatezu. The spell was eventually phased out in the third edition of the Dungeons & Dragons game in favor of a more comprehensive creature-summoning spell.
- In the fantasy video game Baldur's Gate II: Shadows of Amn, the BioWare Infinity Engine equivalent of the "Cacodemon" spell is known as "Cacofiend".
- In the fantasy world Glorantha, Cacodemon is the god of lawlessness and ogres.
- In the Doom video game series developed by id Software, Cacodemons are an enemy, depicted as levitating, spherical, one-eyed monsters. They fire burning projectiles and have appeared in every game of the series, becoming something of an icon for Doom as a whole.
- In Final Fantasy XI MMORPG, the Terrestrial Avatar Diabolos uses a special attack called "Cacodemonia".
- In Anarchy Online MMORPG, a pet that one of the professions can summon is the Cacodemon.
- In Wizardry V: Heart of the Maelstrom, Cacodaemons are large red demons encountered on floor 777.
- In the Pathfinder Roleplaying Game, cacodaemons are many-eyed, tadpolish daemons used as pets by greater ones and as familiars by spellcasters.
- In Smite, there is a set of three Cacodemon skins for the playable God Ymir.
- In Magic: The Gathering, Dread Cacodemon is a card from the Commander expansion.
- In Dungeon Crawl Stone Soup, Cacodemons are large, yellow demons who attack with projectiles and hexes. 
- In the Minecraft mod Lycanites mobs, the Cacodemon appears as a tameable enemy in the nether, and has the same appearance as dooms cacodemons
- Spence, Lewis (2003) . An Encyclopædia of Occultism. Mineola, New York: Dover Publications, Inc. p. 84. ISBN 0-486-42613-0.
- Shakespeare, William. "Act 1, Scene 3". The Life and Death of Richard the Third. Retrieved 19 February 2020 – via shakespeare.mit.edu.
- Francis, Beaumont; John, Fletcher (1647). Comedies and Tragedies. London: Printed for Humphrey Robinson, at the three Pidgeons, and for Humphrey Moseley at the Princes Armes in St Paul's Church-yard. p. 95.
- Wilson, James (1819). A Complete Dictionary of Astrology, in which Every Technical and Abstruse Term Belonging to the Science Is Minutely and Correctly Explained, and the Various Systems and Opinions of the Most Approved Authors Carefully Collected and Accurately Defined. London: Printed for William Hughes, Islington Green, and sold by Sherwood, Neely, and Jones, Paternoster-Row, and by all other booksellers. p. 13.
- de Vore, Nicholas (2005) . Encyclopedia of Astrology. Abingdon, Maryland: Astrology Classics. p. 36. ISBN 1-933303-09-3.
- "Cacodemonic, 1916 - Paul Klee". WikiArt. Retrieved 19 February 2020.
- Stafford, Greg; Richard, Jeff; Petersen, Sandy (2014). Guide to Glorantha. I. Moon Design Publications. p. 153. ISBN 978-0-9777853-7-7.
- "Cacodemon". Doom Wiki. Retrieved 25 September 2016.[better source needed]
- "Eudemons & Cacodemons". Demonology 101. Kelley Armstrong. Archived from the original on 6 April 2006. Retrieved 27 March 2006.
- "Daemon, Cacodaemon" (PDF). Pathfinder RPG Bestiary 2. Illustrated by Tyler Walpole (1st ed.). Paizo Publishing, LLC. December 2010. p. 64. ISBN 978-1-60125-268-5.CS1 maint: others (link)
- Stewart, Todd (2011). "About Daemons" (PDF). Pathfinder Campaign Setting: Horsemen of the Apocalypse: Book of the Damned. 3. Paizo Publishing, LLC. p. 20. ISBN 978-1-60125-373-6.
- "Ymir". Official Smite Wiki. Retrieved 19 February 2020.
- "Dread Cacodemon". Magic: The Gathering. Wizards of the Coast LLC. Retrieved 19 February 2020.
- "Cacodemon - CrawlWiki". crawl.chaosforge.org. Retrieved 9 July 2020.