The Regal Realms is an expansion released September 26th 2012. It introduces new units, Keep and Castle Realms and also the new Policed permission type. Stonemasons build Castle and Keeps and they work the same way as tunnels do, as entrances to new realms. Everyone can attack each other inside these policed realms, except the creator/owner is invincible. You can’t attack them, they can’t be damaged.

Keeps and Castles are expensive, but if you can afford one it gives you a permanent safe base to launch attacks from and a place to call home.