Union

Union is a system to patch and extend Gothic's engine the ZenGin. It allows you to load .dll files - ZenGin extensions created using the Gothic/Union SDK and .patch files - files designed to patch the game's executable. The Union installer also contains the SystemPack a collection of bug fixes and engine edits that improve performance.

Plug-ins

Union plugins are shipped in the form of a .dll library. This library contains the compiled C++ code with the Union SDK and an embedded .patch file.

Union SDK & Gothic API

Union software development kit is a collection of tools and the Gothic API that allow you to create Union plugins and alter the engine's behavior.
Gothic API is a set of 4 interfaces (each for one different ZenGin version) that allow you to interface with the engine, access the engine objects, change their behavior and introduce new classes and functionality.

PATCH file format

The .patch file contains one or more small programs that are designed to change the engine code (game executable). This is usually done to fix bugs. Union plug-ins contain an embedded .patch file and this file usually contains changes to the binary necessary for the proper function of the plug-in.