NiMUD is a periodically updated package of open source MUD software. It has been distributed as "NiMUD", "TheIsles" and "NiM5". It appears in the original Diku Family Tree from usenet and is also mentioned on the official DikuMUD website. The project included what became a popular variant of online creation for Merc DikuMUD, and possesses features adapted from LPC and DuneMUSH. NiMUD also spawned the popular "magic gems" features of some Merc MUDs, who ported the code from early Isles versions. Also, NiMUD instituted the first "Weapon Functions" in a DikuMUD, enabling the auto-decapitating vorpal sword.