Son Dunn, son of the forge, betrayed and mutilated by his companions, is an NPC that I created for a completed DND campaign of which I was the Master. I imagined it as a boxer class, a homebrew I found online. Very interesting as a class, but I think a very competent player is needed, given the moves etc.
However, it's really cool to see how, through the players, a completely secondary NPC can rise to a leading role thanks to the game.