Legend: Nargaster is a swarthy master magician that could wipe out a horde of dragons with one magical sneeze. In every village he has left many a buxom lass heartbroken yet "satisfied". He is considered one of the greatest living legends of the world and where he goes, justice follows.
The Truth: Nargaster is a wimp that knows a few minor magic tricks. His legend is a result of his childhood sweetheart, Grezelda the Bard, who's heart he inadvertently broke. Rather than compose "rage ballads" of his inadequacies, she has built him up to a legend that he can never live up to. The tales have even taken on a life of their own and many great deeds that are accomplished by other heroes are becoming attributed to Nargaster.
Whenever he tried to cash in on his fame with towns, he found himself asked to do magics he is incapable of against threats that would squish him like a bug. And as for the ladies, when faced with the reality of Nargaster they tend to unleash mocking tirades. Nargaster has now been branded as a cheap, weaselly impostor of himself.
Nargaster is not a bad guy. He genuinely does want to help people and will often try to recruit adventurers to help those in need. Unfortunately whenever the heroes are successful, Nargaster's fame grows and the forgotten heroes take it out on Nargaster.
Nargaster would work as a reoccurring npc, always trying to drum up help for some village in need.
He may also have his own character arc: The only way for him to break out of Grezelda's curse is to actually become the Nargaster she has built him up to be. Having the heroes help him to become that person could be a great moment in the game. Heck, maybe they can even get him and Grezelda back together!
Yeah this type of character is fit for a Fantasy campaign and I have been hounding on sci-fi a lot lately, but as I said I have to take my inspiration where I can.