The original edition of Heretic was only available through shareware registration (i.e. mail order) and contains three episodes. A retail edition, distributed by GT Interactive, was titled Heretic: Shadow of the Serpent Riders and features two additional episodes: The Ossuary, which takes the player to the shattered remains of a world conquered by the Serpent Riders many centuries ago, and The Stagnant Demesne, where the player enters D'Sparil's birthplace. A free content patch was downloadable from Raven's website to update the original Heretic to match Shadow of the Serpent Riders.
Each game uses different controls, most DOS games use the keyboard arrows. Some will use the mouse , "Alt" ,"Enter" and "Space bar".