What MUDs Have The Best AI?

Most MUDs have mobiles of very limited intelligence that stand around waiting to be killed and often don’t even bother to remember that you attacked them ten seconds ago.  Some games have more intelligent creatures that actively try to defend themselves and take down the enemy by the most effective means (always fireballing trolls, dispelling undead opponents, etc.)  What MUDs have you played with more advanced/detailed mob AI?  What was it like?

Sure, there are the obvious ones from the Basternae ancestry, but I’m looking for the ‘best of breed’ so I have a standard to measure against.