Expansions

Periodic free updates are released as content patches on an average of three per month since the game's release. These fix bugs, and add relatively small amounts of new content. The patches are downloaded and installed automatically when players start the game software.[46] Larger updates, called expansion packs and booster packs, are available for purchase to further extend the game, typically adding new playable areas, creatures, equipment, and story progression. Expansions tend to introduce large amounts of new content; boosters are considered "too large" for a patch, but "not large enough" to warrant a full expansion