The product was a radio drama version of Jackson's popular Fighting Fantasy novels, and the outcome of the story could be affected by choices the user made, using a touch-tone telephone.

Both games were dungeon crawls, depicting the player's unnamed character progressing through the titular Castle Mammon in an attempt to slay the Demon Prince Kaddis Ra.

Combat consisted of the player being read a description of what their opponent was doing, and pushing a key combination to take action or cast a spell in response.

There was also 'The Black Claw Tavern', a group discussion line which connected with other adventurers calling at the same time.

[2][3] On December 2, 2023, Swedish games publisher Sound Realms announced the return of Steve Jackson's F.I.S.T.