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.