Mythos was a collectible card game for two or more players published by Chaosium and based on the Cthulhu Mythos and the Call of Cthulhu role-playing game. It was first published in 1996, but discontinued in 1997 after a slump in sales. It was succeeded in 2004 by Call of Cthulhu Collectible Card Game, a licensed CCG from Fantasy Flight Games, later transformed into the Living Card Game Call of Cthulhu: The Card Game.
Players choose an Investigator, a double-sized card representing a character archetype from the Mythos. Other cards, including Locations, Events, Allies, Artefacts, Tomes and Spells, are played for various game effects. The goal of the game is to score points by completing Adventures, short story cards which specify other cards or card types which must be played to tell the story. Players can also summon Monsters, who may battle each other, though this is a secondary aspect of the game. It is also possible to eliminate other players by reducing their Investigator's sanity to zero.
The original Limited Edition consisted of starter decks, which included a random investigator card, and boosters released as three themed collections: Expeditions of Miskatonic University, Cthulhu Rising and Legends of the Necronomicon.
The Standard Set included two pre-configured decks, one "Stalwart" and the other "Corrupt".
Two expansions were published in the game's second year: Dreamlands, which introduced other dimensions, especially elements from The Dreamlands cycle of stories; and New Æon, which added modern-day elements drawn from popular culture, including the Men in Black, aliens and time travel.