Chaosium is one of the longer lived publishers of role-playing games still in existence. Founded by Greg Stafford, its first game was actually a wargame, White Bear and Red Moon, which later mutated into Dragon Pass and its sequel, Nomad Gods. White Bear and Red Moon is notable for containing the first published material about Glorantha, later used as the primary setting for the role-playing game RuneQuest, Hero Wars and HeroQuest.
Chaosium and Greg Stafford are also responsible for Pendragon, an Arthurian RPG now published by White Wolf, Inc.'s ArtHaus imprint after a spell with Green Knight Publishing. Other games of note include Mythos, Elfquest, Worlds of Wonder, Superworld, Hawkmoon, and the frequently forgotten Prince Valiant.
Several notable RPG authors have written material for Chaosium, including Steve Perrin, Sandy Petersen, Lynn Willis, David Conyers, Ken St. Andre, and Arduin creator David A. Hargrave.
In the mid-1980s, Chaosium entered into a complex arrangement with Avalon Hill to publish RuneQuest material while Chaosium maintained editorial control over Glorantha-based material for the game (which Avalon Hill would publish). While this agreement reportedly kept the company in existence, it also left RuneQuest moribund, leading to products of questionable quality, long gaps with no products published at all, and, eventually, the death of the game altogether.
In response to the collectible card game craze, Chaosium released the Mythos CCG. Initially it was a great success, but the crash hit hard.
In the late 1990s, Chaosium effectively split up into various successor companies, each maintaining its focus on a few of the company's products. Green Knight Publishing formed to focus on Pendragon, Chaosium "proper" retained Call of Cthulhu, Stormbringer, and Mythos, while Greg Stafford founded Issaries, Inc. to publish HeroQuest and focus on bringing new Glorantha related material into print. Also, Wizard's Attic (no longer in business) was formed in order to act as a fulfillment house. Charlie Krank became president when Stafford left.