Standalone expansion

An expansion pack, expansion set, supplement, or simply expansion is an addition to an existing role-playing game, tabletop game or video game. These add-ons usually add new game areas, weapons, objects, characters and/or an extended storyline to an already released game. While board game expansions are typically designed by the original creator, video game developers sometimes contract out development of the expansion pack to a third-party company, (see Hellfire for Diablo), it may choose to develop the expansion itself or it may do both (Ensemble Studios developed the real-time strategy game Age of Empires III and the first expansion called the WarChiefs itself, but contracted Big Huge Games for the second expansion pack, the Asian Dynasties). Board games and tabletop RPGs may have been marketing expansions since the 1970s, and video games have been releasing expansion packs since the 1980s, early examples being the Dragon Slayer games Xanadu Scenario II and Sorcerian.

The price of an expansion pack is usually much less than that of the original game. As expansion packs consist solely of additional content, most require the original game in order to play. Games with many expansions often begin selling the original game with prior expansions, such as The Sims Deluxe Edition (The Sims with The Sims: Livin' Large). These bundles make the game more accessible to new players. When games reach the end of their lifespan, the publisher often releases a 'complete' or 'gold' collection which includes the game and all its subsequent expansions.

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