The design and command structure of Dark Castle is superior to most other muds that I've played. The environment is brutal as far as playerkilling and real-deaths, which makes it that much more intense.

DC has a long history and used to have around 100 active players on at any given time, but the recent addition of Variable Experience changed that. The new experience system strongly favors grouping and detrimentally hinders solo players. (Even as an established player, I find it impossible to solo and get any worthwhile experience.) This results in established players dominating while new players have little hope of getting anywhere. DC has tons of unique features that have the potential to make it a great mud again, but the experience system overshadows most of the positive changes, especially for new players.