Hexen: Deathkings of the Dark Citadel, an expansion pack for Hexen, was released on January 1, 1996. Hexen extended the Doom engine in many innovative ways: larger levels, some doors that opened three-dimensionally, pulsating lights, triggered sounds, and other features. Unlike previous games, which had relied purely on MIDI for music, Hexen could also play tracks from the game's audio CD. It also popularized the ' hub system' of level progression in the genre of first-person shooter games and featured some architectural elements that could move horizontally or rotate.
Hexen uses a modified version of the Doom engine, which (like in Heretic) allows the player to look up and down, network play with up to 8 players, and the choice of three character classes. The first Serpent Rider, D'Sparil, was the final boss of Heretic and the third, Eidolon, would later appear in Hexen II. The main goal of the game is the destruction of Korax, the second of a trio of demon brothers known as the Serpent Riders, who has taken over the world of Cronos. Hexen: Beyond Heretic (or simply Hexen) is a first-person shooter computer game developed by Raven Software, published by id Software, and distributed by GT Interactive beginning on October 30, 1995.