This is a Slimefun addon, that makes "The End" world less boring. You can explore this world, find some wild purple trees, or just came here with GEO Miner to gather resources.
You can now download releases on this page.
Endrex uses Maven to build, so you'll need Maven
cd Endrex
mvn package
cd target
cp "Endrex v1.1.0.jar" "../../testServer/plugins"