[Orrin]

Many MUDs allow for players to form their own organisations, whether called guilds, clans or something else. Usually your organisation will get some kind of building in the game world they can use as well as a member only communication channel. There may be special member ranks and privileges or access to member only equipment as well.

I suppose I should plug my own game at this point and say that will feature player cabals that you can form with your friends.

Even if your favourite MUD doesn't offer this feature it is worth asking the administrators to consider adding it. It's a lot easier to add something like this to a MUD than it is to an MMO.