User blog comment:SpiritofRevenge130/Usefull NPC/@comment-4113369-20121108153140

Azura. Her star is probably the most useful item in the entire series (even more so when you blacken it in Skyrim). She also gives you several other goodies throughout Morrowind. Not technically an NPC though. In technical terms, she's an "activator", I think the term was. Haven't opened a TES construction kit in a while, so I'm not sure.