This is a map that I created for @SleepMaster for testing custom made enemies and bosses. I figured I would share it so anyone else who might find it helpful can make use of it. This is not custom content it is only for testing.
There are four areas; the hub, the end of the Arid Hills, The Devils Footstool, and a piece of the Arid Caves.
The hub is the first place you spawn and has vending machines, a New-U station and doors which access all three testing areas, just run through these doors to be teleported.
When you enter these arenas enemies will spawn except for the Devils Footstool which requires you to use the blue crystal to spawn a boss enemy, the red crystal will delete the spawned actor if needed be.
Any time you leave one of these areas you will run through a trigger volume which will delete all spawned enemies in the respective location and bring you back to the hub.
Keep in mind this map is only for testing custom content and is not actual content itself.