It shares art and characters with FFG's other Cthulhu Mythos products Arkham Horror and Elder Sign.

It was designed by Eric M. Lang as a more accessible introduction to gaming in the Mythos environment and to provide a fast and lively interplay with the usual elements of the mythos (e.g. arcane tomes and secrets, paranormal investigations, the elder gods and their terrible servants, dark sinister plots, inhuman conspiracies, and dangers from beyond the stars).

In the Living Card Game format, the original story line was penned by Nate French, with the help of Dan Clark.

Players typically assign character cards to stories, to win struggles and gain these success tokens.

Additionally, the first player to run out of cards to draw from loses the game, making deck destruction another potentially effective strategy.

Released approximately once a month, these expansions were designed to increase the players' card pool in a balanced and affordable way.

The initial printings of the sets included varying quantities of each card to echo the rare, uncommon, and common rarities of the original game, and this distribution may still be found in some out-of-print packs.

The Asylum Packs proved to be very popular, encouraging Fantasy Flight to convert the entire game into the LCG format.

Fantasy Flight continued printing monthly Asylum Packs, arranged into six-piece cycles, for several years.

In July 2012, Fantasy Flight announced that they would switch to a new distribution model: instead of the near-monthly Asylum Packs, there would be one 165-card deluxe expansion every four months, beginning with Seekers of Knowledge.

The kits include alternate art versions of existing cards to be used as prizes, as well as a unique deck box, promotional poster, and two sets of specialized wound tokens.

On the September 22, 2015, it was announced that Fantasy Flight Games would cease all tournament support and stop developing new expansions after the 2015 World Championship.