Hexen was released in 1995 by Id Software. It is developed by Raven Software, and is the sequel to Heretic released in 1994.
The story of Hexen follows the tale of D'Sparil's defeat in Heretic. Hexen takes place in another realm, Chronos, which is besieged by the second of the Serpent Riders, Korax. Three heroes set out to destroy Korax. The player assumes the role of one such hero.
One of the new feature introduced in Hexen is the choice of character class. We can choose to be a fighter, cleric, or mage. Each character has unique weapons and physical characteristics, lending an additional degree of variety and replayability to the gameplay. The fighter relies mainly on melee attacks and is tougher and faster than the other characters. The cleric uses specialized weapons, some of which have limited range or healing effects. The mage uses long-range weapons, whose reach is counterbalanced by dealing relatively little damage and the fact that the mage is the most fragile of the classes.
Hexen also introduces the concept of "hub" levels to the series, wherein we travel back and forth between central hub levels and connected side levels. This is done in order to solve larger-scale puzzles that require a series of items or switches to be thrown. The player must traverse through a hub in order to reach a boss and advance to the next hub.
On the technical side, Hexen uses a modified version of the Doom engine, which allows jumping, network play with up to 8 players and the choice of three character classes. It also popularized the "hub system" of level progression in the genre of first-person shooter games.
Unlike previous games, which had relied purely on MIDI for music, Hexen is also able to play tracks from CDs. The game's own CD contained soundtrack in audio format that was exactly the same as the game's MIDI soundtrack but played through a high quality sound module. However, the most significant improvement was the addition of wall transition, rotation and level scripting.
You can download Hexen here.