The Construction Set (abbreviated CS) was the software development kit (SDK) that was shipped with Morrowind on a second disk. It is the same tool used by Bethesda to develop the game, Tribunal, Bloodmoon, and the official plugins. The CS can be used to change everything in the game that is not hardcoded. This ranges from: items, new lands, interiors, and even scripts. It saves changes in the .esp format, which is a proprietary format use by Bethesda for their Elder Scrolls and Fallout games. The .esm file format can also be loaded by the CS, however it cannot save in the format. Modders have created tools to allow them this functionality. The Construction Set is not an easy tool to learn to use, with many pitfalls and issues to avoid. Fortunately, over the past twelve years, the community has creating countless tutorials and guides to aid both new and veteran modders in creating the best mods that they can.
- Main article: GMST Contamination
GMST Contamination is what happens when the CS automatically adds 72 Game Settings (GMSTs) to a mod. This only happens with the updated CS for Tribunal and Bloodmoon. If a mod does not have either Tribunal or Bloodmoon as one of its parent files, then the 72 GMSTs will be added. This behaviour wouldn't be a problem if the values for the GMSTs were not incorrect. As such, using a contaminated mod may cause issues and strange behaviour with a player's game. Because of this, it is recommended that modders always check for contamination before releasing their mod. While it is recommended for players to also check the mods that they download.
Many tools have the ability to clean mods:
Unfortunately the Construction Set was not included with the Morrowind Steam GOTY version (with patch 1.6.1820). This is the same regardless of whether the physical disk was bought or if it was bought straight from the Steam Store. To fix this, you can download the necessary files from here.
Once downloaded, you will need to extract the files into your main SteamApps\common\Morrowind folder.