This is a survival server that went full anarchy. It used to be a normal SMP but most of the players left. Now the whitelist is gone and it is just chaos.
There are lots of old builds around and people can grief them and steal all the loot. Nothing is really safe and the whole idea is that the strongest players survive.
If you get stuck in the lobby you just type slash server smp to join the real world and jump into the madness.
