Daedalus extenders
The default scripting language Daedalus can be quite limiting. Over the years the community created quite a few extenders to, well, extend the functionality. Before Union came along, the standard to interface with the engine was the script library Ikarus and a collection of packages LeGo built on top of that. Not so recently, an additional script packet was made (and is actively being worked on) AF Script Packet that offers even more functionality and is built on top of Ikarus & LeGo.
With the adoption of Union and plugins the Union system can use a new extender emerged called zParserExtender. Other Union plugins can, of course, implement their own external functions. A lot of scripts are also scattered on the Gothic forums, and documentation of some of them can be found in the Standalone section.