In 1997, developer Frictional released Amnesia for the PC, Mac, Amiga, and Atari Jaguar by using the Game Maker development software. The game was updated to the Windows 98 version in 1999. The development of the original version was funded entirely by the development team. The team wrote the game in a month and released it the following January. Frictional released the next major version of the game the following June. Amnesia was released on the Mac and Windows in July 1999 as well as for the Atari Jaguar in September. The Amiga version was released later that year. Amnesia was published by THQ in North America in 2000 and by Rising Star Games in the United Kingdom in 2001. Frictional released the first Director's Cut in April 2003. Designed as a way to show off the increased graphics and production values, it was released to positive reviews. In October 2010, the game was released for free via GamersGate as the Amnesia: Rebirth expansion for the original game. The expansion was accompanied by the Amnesia: A Machine for Pigs expansion created by Chris Bateman, which allowed players to build a pig body for their character and create pig versions of nearly every monster in the game. Amnesia: Rebirth was also available on PC for a limited time.
In 2005, a fan-made sequel, The Dark Descent, was released by Frictional. The game was based on the Amnesia engine but featured a new storyline. The game's setting, The Factory, was inspired by the real-life factory where Thomas Rowe worked and where the events of the game occur. It is also set within the same world as the original Amnesia. The game was developed by Kevin Martin, who at the time was hired by Frictional.16 It was released in 2005 for Windows and Mac.18 A sequel, A Machine for Pigs II, was released in September 2006 as a separate game by Frictional. The sequel was developed by an external developer, GluWareHouse 827ec27edc