Darcsyde Productions is a role-playing game publisher which has produced the Corum supplement for the ChaosiumStormbringer (aka Elric!) RPG and are currently working on a Hawkmoon-themed supplement for the same games.
In addition, Corum, a supplement to the Stormbringer rules, was published in the fall of 2001 by DarcsydeProductions.
In order to underscore this, Chaosium produced the Worlds of Wonder supplement, which contained the generic rules and several specific applications of those rules to given genres.
Superworld, specifically, began as a portion of the Worlds of Wonder product.