They’re archives of the old Dark Gaming.
Before dimensions were implemented in 2017, Dark Gaming composed of a single world that reset every so often.
29 June 2017 - TSL and the Dimensional Restructuring
This was a dimension that was removed in 2019. In Autosurvival, you could create your own world, and it would be automatically managed and hosted for you. You’d be granted all TShock permissions on that world, and you could invite others to it.
If I recall correctly, Zombies Map Builders edit their world here.
This is just a dimension for testing.