Ultima Underworld 2: Labyrinth of Worlds was released in 1993, and featured an upgraded version of the 3D engine of the original Underworld. Underworld 2 is not always considered a canon Ultima, although unlike its predecessor it does tell a somewhat important part of the Ultima story following Ultima 7 and leading up to Serpent Isle.

Underworld 2 sees the Avatar and the leaders of most of the towns of Britannia entombed in a blackrock dome by the treacherous Guardian inside the castle of Lord British. The Avatar must find a portal to another world, this one already subjugated by the Guardian and enslaved by his anti-Virtues, and from there journey between worlds to find a way to break the massive dome.
Underworld 2 Revival
Lord British's Throne Room
Produced by: dforger
Website: Underworld 2 Revival
Releases:
* Shared Files (Nov. 11, 2002)
* Windows Build (Nov. 11, 2002)
* Source Code (Nov. 11, 2002)
* User Manual

This remake of Underworld 2 for Windows has not been active in some time, and seems only partly developed.

However, its SourceForge page is still active, and as such the latest build and source code are available.

LOW - Labyrinth of Worlds
Lord British
Produced by: Marc A. Pelletier
Website: LOW @ Sourceforge
Releases:
* LOW 0.4 (Windows)
* LOW 0.4 (Linux)
* LOW Source
* LOW 3D Models
* LOW Music
* LOW Sounds
* LOW Data Files
* LOW DLL Files (Windows)

LOW is a cross-platform re-write of Ultima Underworld 2 "from the ground up". While it appears that development on this project has paused, its Sourceforge site is still active and there is source available for download, as well as a host of demos for different systems.

The latest version of this remake (dated 2002) features 3D models of the characters.

Ultima Underworld II Patch
Produced by: Origin Systems Inc. (defunct)
Website: Origin Systems (redirects to UO site)
Releases:
* Official Patch

This patch corrects several plot-stopping bugs in the disk-based version of the game only. All versions of the game that shipped on CD should have the patch installed already.

Underworld in NT
Produced by: Moscow Dragon, Sir Cabirus Dragon

Website: Sir Cabirus
Releases:
* NT Patch

Windows NT (and NT-derived systems like Windows 2000) are not always game-friendly platforms. Moscow Dragon came up with a patch that allowed Underworld 2 to run under the NT/2000 environment, and this was later expanded upon by Sir Cabirus Dragon to support Underworld 1 as well.