Keys are a recurring feature of the Dragon Quest game series series. Keys appear in all main-series games and most spinoff games. From time to time over the course of a Dragon Quest game, the player will encounter locked doors that can only be opened with the correct key. Usually, one key can open all the associated doors of its type, though in some games they are one-use items and other keys must be found or purchased to use that type of key again. Typically the player will find higher- and higher-level keys throughout the course of the game, with higher-level keys working on all levels lower as well, making old keys obsolete. Eventually, the party will find a "Magic key" and then an "Ultimate key" capable of opening all doors everywhere.