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, and/or an extended storyline to complete 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 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.