Just a heads up, at the end of the guide I've included optional edits and even linked mods for the game, make sure to check these out if you're interested.

The version of DOSBox shipped with TES Redguard is not compatible with 3DFX wrapping and needs to be changed first.

Navigate to your installation folder in steamapps\common\The Elder Scrolls Adventures Redguard

Rename the "DOSBox-0.73" folder to anything you want. I'm calling mine "backup".

Download the latest DOSBox SVN Daum build as a 7z file from this link[ykhwong.x-y.net]

Extract the contents of this archive to a folder somewhere and copy this folder to your Redguard installation folder. Rename this folder to "DOSBox-0.73". This will cause steam to run the Daum version of DOSBox when launched.

Finally, copy the "rg.conf" configuration file from the DOSBox backup folder you created earlier and paste it into the new "DOSBox-0.73" folder

Next we need to switch to the 3DFX version of TES Redguard. Normally, you would reinstall the game using the installation disc (which you won't have unless you are very lucky or use rom sites) however it is only necessary to copy over and remove some files, which I will provide.

The GOG version of the game contains the necessary files to run TES Redguard in 3DFX mode
Side Note: I recommend launching the game in either full screen or windowed mode now to ensure everything is still working before proceeding.

First, navigate to the "Redguard" folder in your installation folder, this is where the game files are located such as "Redguard.exe".

Delete the folder named 3dart as this contains the graphical data for the software version of the game.

Download the files needed to upgrade the game to 3DFX here[drive.google.com], then just copy all the files from the archive to the "Redguard" game folder (where Redguard.exe is located)

Next, we need to simply edit some lines in the games configuration files.

First, open the "rg.conf" file located in the DOSBox-0.73 folder using notepad or notepad++ etc.
(Please note, whilst highly unlikely the game may receive future updates changing the configs so the line numbers may change).
Scroll right to the bottom and paste the following underneath the line "keyboardlayout=auto" on line 223:

[glide]
# glide: Enable glide emulation: true,false.
# grport: I/O port to use for host communication.
# lfb: LFB access: full,read,write,none.

glide=true
grport=600
lfb=full

Finally, in the autoexec section at the very bottom, change "rg" to "rgfx"

By the end it should look something like this

First, delete (or rename) the "glide2x.dll" file from the "DOSBox-0.73" folder

In order to run 3DFX games in Glide on modern systems, we need to install the nGlide wrapper.
Download the exe from Zeus software here[www.zeus-software.com], run and install it.

Next run the nGlide Configurator from the windows start menu and set it up as shown in the screenshot below for a basic setup. (The options in this application may change with newer versions but it's roughly the same with each update)
Feel free to play around with these settings. Outside of the guide, I set my refresh rate to 60hz (144hz seems overkill for a 90s game) and my resolution to my monitor's resolution, however this also needs to be changed in the "rg.conf" file if you choose to.

That's it! Redguard should be good to go in 3DFX Glide mode, giving the game a massive visual improvement. Run the game and test it out for a bit, if you see the 3DFX splash animation at the start of the game load, it's all good to go. You can also confirm this by looking in the settings and there should be no options for editing the display settings (this is now handled by the nGlide Wrapper).

Feel free to make changes to the game configuration ("rg.conf"), I won't get into this in detail but ensure "memsize=63" under [dosbox] and a few changes I recommend are;

Under [cpu] change core=auto to core=dynamic - This will provide a large performance boost which may be needed as the game now is more graphically demanding, however some users have reported this setting casing their PCs to crash etc so be cautious.

Under [glide] Add the line "splash=false" - This will disable the 3dfx splash animation when starting, just a small quality of life change.

If you plan to use a controller, under [joystick] change timed=true to timed=false - This fixes a bug where Cyrus will constantly move with a controller connected.

Last but not least, as surprising as it is a wiki user (Dillonn241) has actually created a mod manager for the game which comes with 2 mods available for instillation, it also allows you to edit textures etc. But the mods the come with the program are;

Unofficial Redguard Patch - General Bug Fixes, mainly subtitle fixes

Sea Serpent - Restores cut content where a giant sea serpent spawns at the Spire in game

By all means check it out here[en.uesp.net] if you for some reason want more out of this game

Thank you for reading my guide and enjoy playing this terrible game with some fresh visuals :)