Ultima Underworld Series - Mobygames

Ultima Underworld games are spin-offs of the main Ultima series, and are part of the Ultima Universe. Unlike other spin-offs (such as Worlds of Ultima), Ultima Underworld games are connected by setting and plot to the main Ultima games.

The first game, Ultima Underworld: The Stygian Abyss (1992), is notable for being the first role-playing game (and one of the first games in general) with true 3D environments. Unlike the games in the main Ultima series, it was set entirely in a vast underground area, and featured action-based combat. Similarly to other Ultima games, it offered non-linear story progression and exploration possibilities, as well as detailed interaction with the game world.

The sequel, Ultima Underworld II: Labyrinth of Worlds, was released in the following year. Having very similar gameplay, it featured a larger game world with more diverse locations.