Armageddon struck the land of Erathia, threatening to destroy the entire planet. The people fled through magical portals to another world, a fresh new world ripe for colonisation.

Gameplay consists of developing towns and moving armies around an isometric grid-based fantasy world, capturing resources and battling enemies. Combat takes place on another screen, where the two sides line up and take it in turns to act. There are six campaigns to choose from as well as a host of single scenarios. Differences from previous games include more customisable heroes who can specialise in more fields, the ability to have many or even no heroes in an army, and a new way of organising spells and classes.

Long ago, the universe came under attack from terrible demons known as the Serpent Riders. The world of Thyrion was taken over by Eidolon, the strongest of the three. His grip on the world is maintained by his underlings, the Four Horsemen of the Apocalypse.

Continuing the Hexen/Heretic saga, you have the task of going it alone against the Horsemen and eventually Eidolon himself. With a choice of four heroes, Paladin, Crusader, Assassin or Necromancer, you fight your way across the world's four continents in a 3D shoot-em-up style based on the Quake engine. Each character class has their own arsenal of four weapons, and the large collection of powerups and other artefacts are essential to survival. As you work through the hub level system you must do combat with demons and solve simple "door/key" type puzzles. Each continent has a different theme and ends with a Horseman boss, and they must be tackled in order.

The game of the book, H2G2 roughly follows the plot as you wake up as Arthur Dent on the Earth's final day before being demolished to make way for a hyperspace bypass. With the help of Ford Prefect, you must save your house and flee the planet, survive on the Vogon ship, and finally end up on the Heart of Gold. In order to move around and solve the puzzles, commands like "north," "drink beer," and "panic" are entered via a textual interface that actually has a rather advanced parser.

Things have been happening at the secret labs of DBR Corporation, under the direction of the mysterious Dr. Curien. The researchers have been slowly disappearing for unexplained reasons, and it is up to special agents Rogan and G to investigate. They turn up at the isolated mansion and it doesn't take long to realise that something is definitely amiss, as the grounds are crawling with what appear to be the undead.

Gun in hand, you (and maybe a friend) must take on the zombified hordes as you fight your way through the mansion and the labs beyond. Play is on rails, but a number of different routes are available depending on which beasties you slay and how quickly you slay them. All paths coincide at the major bosses, culminating in a showdown with Curien's most powerful creation. Not shooting the likes of chainsaw-wielding psychopaths, lightning-fast monkeyesque creatures, or slithering maggots in time will lose you a life, but they can be regained by finding and rescuing scientists. In the home versions you can choose a character, determining statistics such as health, bullet damage and clip size.

You are trapped in the House of Usher and the only way out is by completing a number of challenges, one in each room. You have a very tight time limit; the timer counts down from 999 all the way through the game. Fortunately, not all of the rooms need to be completed. You can choose which ones to attempt, with the exception of the final rooms, and each poses a different challenge. You might have to avoid broken floorboards, jump cannon shells, or navigate a disappearing staircase. Contact with a nasty or falling too far will result in instant death, and you are sent back to the lobby.