I started to play Holy Mission 1996 at university and have to admit that no other game (Neither MUD nor any modern genres) ever managed to enthrall me as much. My absolute top features are

-) Quite balanced classes

-) Challenging PVE Fights and quests

-) PVP (Every time an unbelievable Adrenaline rush – My smartwatch even assumes that I am doing some sportive activity!!!)

-) The overland map between the zones!

-) Nice community (Always someone online, helpful)

-) Ongoing Development (where community feedback is taken very serious)

-) All these little details that have been added over more than 25 years, I still find new things most time I play

-) The new Homepage which just went live http://www.holy-mission.org (I made it, so I assume this point does not count)

-) The nostalgic feeling I get every time knowing that this game is up since 1992, and have virtual friends there since I started to play