The easiest way to mod the game is via the data files, most of which end with .json after the format they are stored in. You can find most of these under data/jsons. We have a simple textual guide to what appears in each file and what those values mean.
A variety of tools have been developed to make modifying and improving Cataclysm even easier. A few of these are reaching a point in the development cycle where they are worth being shared with the public, and are linked and described below!
A graphical tool for editing the game JSON files quickly and efficiently. Requires .NET Framework 4.0