CaW is a server a few members of the GC community are already playing on. It's a factions server, so you could go out and found your own or join one of the existing ones and get in on that sweet sweet political tension. It has a few plugins that effect PVP and add things like drawbridges and portcullises. CoG is a high-ranking dwarf. The Dwarven Empire is the oldest and best established faction on the server. I run the Mailmen with Aumn, a much newer faction that plans to construct rail lines and roads all across the Overworld and Nether to bring people together. Eventually.
You need to be whitelisted to join. Information on that is on the forums:
The Mailmen built the Swamp Castle. Except it wasn't the Mailmen back them, it was the town of Deltaria in Prugundy. Which was a nation for a while. That was a pretty big mess, the Deltarian Rebellion. What I'm trying to get at is that no dwarf has ever built something as cool as a Swamp Castle.