Underworld Revisited

Underworld Revisited

An open-source reimplementation of Ultima Underworld: The Stygian Abyss (1992) in Unity, built on the original game data. The goal is full gameplay parity with the original, plus an optional modern render mode. Support for Ultima Underworld II is planned for later.

You need your own copy of Ultima Underworld - the GOG.com version ("Ultima Underworld 1+2"); other releases are not supported (see Requirements). This repository contains no game data: no graphics, sounds, texts, maps or executables of the original. Everything is read at runtime from your installation. The only exception are the screenshots, which show the original's artwork.

To play, download the latest release for Windows or Linux from the Releases page - see Installation.

This project is not affiliated with or endorsed by the owners of the Ultima Underworld rights. Ultima and Ultima Underworld are trademarks of their respective owners. Underworld Revisited is a free, non-commercial fan project: it is not sold, and no donations are accepted.

Contents: Screenshots - Features - Requirements - Installation - Controls - For developers - How this was made - License

More: Controls - All screenshots - Building - Translating - Roadmap - Third-party notices

Screenshots

The classic interface at 4:3, Palette mode, with the modern font.

Palette mode	Remastered mode
Light computed like the original, the help window beside the view with a live map.	The same spot lit by URP, with relief and glow.

The modern control scheme: the rune panel at the left, the character panel and the bags at the right, the action bar below.

Classic Wide	Classic Modular
The modern scheme in the original's frame, widened to a wide screen.	The original's pieces as parts of their own over the whole view.

More in the screenshot gallery: the world at the original's resolution, the Palette effects, both fonts, the layout editor, conversations and trading. The screenshots show the artwork of the original game, which belongs to the owners of the Ultima Underworld rights. It is shown for illustration only and is not covered by this project's licence.

Features

Built and largely confirmed against the original, and played through from character creation to the end sequence. Open points are listed in ROADMAP.md.

The game

• The nine dungeon levels with their objects, doors, locks, traps and triggers; the 3D models (barrel, chest, chair, shrine, bridge, portcullis ...) read from UW.EXE
• Combat with the original's tables, magic with runes, and the creatures with their goals, attitudes and group alarm
• Conversations, running the original conversation bytecode, including trading
• Character creation, inventory and paperdoll, automap, sleeping, hunger and fatigue, the endgame with talismans and the void
• Save games compatible with the original's, in UNDEROM1\SAVE1 to SAVE4
• Intro, dreams and the end sequence from the original's cutscene files, with speech
• The motion of the player, the creatures and thrown things as the original's own code, run call by call as the original did or as a precise, frame-rate independent computation of the same rules (Motion)

Graphics

• Palette mode computes light like the original through SHADES.DAT and LIGHT.DAT; Remastered lights with URP and adds relief, specular highlights, glow, shadows and torch lights - each switchable on its own
• Effects of the port's own for the Palette mode that keep every pixel a colour of the original's palette: ambient occlusion, grime along the walls, wall depth with its shadow, darker joints, ground shadows, glowing lava and flames, and light sources lighting their surroundings by the original's light table. Off by default, with the presets Subtle and Full
• The world at the original's resolution or a multiple of it up to 4x, with hard pixels while the interface stays sharp
• The classic interface at the original's 4:3, or widened to a wide screen with the frame's stone grown anew instead of stretched; a slider for the view angle

Sound and music

• AdLib music and sound effects through an OPL2 emulation (a C# port of the YM3812 core of Aaron Giles' ymfm)
• The music's MT-32 version on General MIDI, with a soundfont that comes with the game
• The same music on the Roland MT-32 itself, emulated by Munt - with the ROMs of a real unit, which you supply (see Installation)
• Recordings of the music you supply, one file per piece, in place of the synthesizer

Controls and interface

• Two control schemes: the original's mouse-pointer steering, and a modern scheme of the port's own with free mouse look, WASD, an action bar, bags, a character panel and a rune panel built from the original's artwork, and a layout editor to move and size every part
• Interface presets for the modern scheme: Modern; Classic Modular, the original's own pieces (compass, message scroll, power gem, flasks, rune tablet, stats panel, character page with the original inventory) as parts of their own; Classic Wide, the original's frame widened to the screen; or a layout of one's own, which can start from any preset
• A gamepad in both schemes, with a pointer on the stick for every window, a letter grid for typing, glyphs for Xbox, PlayStation, Nintendo or the Steam Deck, and every button rebindable
• A help window beside the view: stats with the hidden values, a live map, notes kept with the save game, spells, mantras and the game's manual
• A modern readable font, and dealing the attribute points at character creation yourself instead of rolling them - each of these additions optional
• Languages: the port's texts in English or German, chosen in the Game window and switched at once; the game's own texts can be translated by language files (Translating)
• Two looks for the game's own windows: Stone, in the colours of the game's icon (the default), and the plain one
• The rule set: an optional rules.json in the UW1 folder beside the settings changes the game's numbers - combat, magic, creatures, motion, trade and more, and the original's quirks as switches. Docs/rules-template.jsonc in the release package (or uwdump rules-template) lists every key with its default and meaning; without the file the game plays as the original

Requirements

• Windows 10 or newer (64-bit) with a DirectX 11 graphics card. It is the system the port is developed and tested on.
• Linux (64-bit, x86-64, Vulkan or OpenGL 4): part of every release since 0.3.0, tested in a Kubuntu virtual machine and far less than the Windows version. macOS is untried. Reports from other systems are welcome.
• Ultima Underworld 1 from GOG.com ("Ultima Underworld 1+2"). Only this version is supported: some data (3D models, their colours) is read directly from the game's executable at build-specific offsets, verified against the GOG UW.EXE (547,248 bytes). Other releases (original floppy, CD, other stores) may differ and are not supported.
• Unity 6000.6.0f1 (Unity 6), Universal Render Pipeline - only to build it yourself.

Installation

First install Ultima Underworld from GOG.com ("Ultima Underworld 1+2"). Then:

1. Download the latest release from the Releases page: UnderworldRevisited-<version>-win64.zip for Windows or UnderworldRevisited-<version>-linux64.tar.gz for Linux.
2. Unpack it into a folder of its own.
3. Start UR.exe (Windows) or UR.x86_64 (Linux). Should Linux refuse to run it, the executable bit got lost on the way: chmod +x UR.x86_64 in that folder, once.
4. The game looks for your GOG installation in the usual places (listed in Building). If it does not find it, it asks for the folder: choose the one that contains game.gog. The choice is remembered and can be changed later in the menu bar of the main menu (Game > Game folder...).

Nothing else needs to be installed; the package brings its own runtime. On the first start the game files are extracted from game.gog once into a local cache; nothing is written to the installation. Save games are read from and written to the installation's UNDEROM1\SAVE1 to SAVE4, so they can be exchanged with the original game.

Music. The Sound menu chooses what plays the music: the AdLib (as most heard it in 1992), General MIDI, or the MT-32. For the MT-32, put the control and PCM ROM of your own Roland MT-32 or CM-32L into the folder the Open folder button there opens; they belong to Roland and do not come with the game. The menu shows which ROMs were recognised.

Music from recordings. Under Music from recordings in the same window, your own recordings of the music play in place of the device, one file per piece in the folder its Open folder button opens (UW1/Music beside the settings). Name each file by the number of the game's piece (UW01.XMI in its SOUND folder is 01): 01 the introduction, 02 to 04 the levels, 05 to 07 combat, 10 Armed, 11 Victory, 12 Death, 13 Fleeing, 15 Maps and Legends, as .ogg (Ogg Vorbis) or .wav. A piece without a recording plays on the device. The high-quality remake by Pieces of 8-bit (on Nexus Mods, made for Hank Morgan's UnderworldExporter) uses these names: the files of its UW1music folder can be copied in as they are.

Controls

Two schemes, both complete: the original one, where the visible mouse pointer steers the walking as in 1992, and a modern one with free mouse look, WASD and an interface of its own. Shift+F2 switches between them at any time, and so does Game in the menu bar. A gamepad works in both.

The help window (Tab) has a Controls tab with the keys of the scheme in force, as you have bound them; keys, mouse buttons and gamepad buttons can be changed under Controls in the menu bar at the top edge. The full tables, the gamepad layout and the motion options are in Docs/CONTROLS.md.

For developers

How to build the game yourself, pack a release, and use the engine-free layer (Assets/UWDataImport, buildable with the plain .NET SDK) and its tools is described in Docs/BUILDING.md. Before building, the self-check tells whether your copy of the game works with this port:

dotnet run --project Tools/UWSelfCheck -- "C:\GOG Games\Ultima Underworld 1"

How this was made

I have been a fan of Ultima Underworld ever since it came out in 1992. In 2012 I came across uw-formats.txt, a text file describing the game's data formats, more or less by chance, and thought: why not give it a try? That was the start of this project, but I never had the time or the experience to take it further. In 2026, with the help of Claude (Anthropic's AI model, via Claude Code), I picked it up again. Since then the code has been written by Claude; I decided what to build, tested every behaviour against the original game and confirmed or rejected the results.

Thanks

This project would not be where it is without hankmorgan's work. His UWReverseEngineering project, a disassembly of UW.EXE with named routines and a large guide to the game's mechanics, is where most of the rules here were read from: the motion code, the creature AI, traps, magic and much more. His UnderworldGodot, a recreation of both Underworld games, provided many formulas and data tables (see THIRD_PARTY_NOTICES.md), and his earlier UnderworldExporter showed long ago that the game can live in Unity.

Thanks to abedegno for Underworld Exhumed, a decompilation that rebuilds UW.EXE byte for byte from readable source. The rules here are checked against it, and many of them were corrected that way. Nothing of its code is taken into this project.

Thanks also to the authors of uw-formats.txt, where this project started.

The application icon (Art/Icon/ur-icon.svg, rendered to Assets/UWIcon/UWRIcon.png) was also made with generative AI (Claude). It shows the runes uruz and raidho (U and R), drawn after the historical Elder Futhark; nothing in it is taken from the game.

License

Underworld Revisited is released under the MIT License, see LICENSE. Parts are derived from other projects under their own licenses, see THIRD_PARTY_NOTICES.md.