The latest - very interesting - addition to Batmud is HC Batmud. The difference to normal Batmud is that if your character dies, it really dies; no resurrections, no raise deads, it's game over, start over.
Naturally the increased difficulty has some compensations eg. the character stats are better than in normal Batmud. Also, the first player to reach certain experience amounts will be awarded with insane amounts of "task points", with which the player may buy boons (sort of blessings that increase the character's stats, skills/spells, makes the character cast his/her spells faster etc).
HC Batmud can be found at: bat.cs.hut.fi port 2223.