Development on an expansion pack began shortly after the release of Titan Quest, with preparatory work happening during the final stages of the main game's development. The expansion, Titan Quest: Immortal Throne, was first announced in late 2006 and eventually released in March 2007. Over eleven years later, a second expansion was released. Titled Titan Quest: Ragnarök, it was released on November 17, 2017 exclusively for the Anniversary Edition. A third expansion subtitled Atlantis was released in May 2019. It included new challenge modes and an in-game casino. PS4 and Xbox One versions of both expansions were released in March 2020. Both Ragnarök and Atlantis were developed by Pieces Interactive. A fourth expansion, Eternal Embers, released in December 2021. Eternal Embers was developed by Digital Arrow.
