Captain Nemo is one of the literary world's most famous
enigmas. He is the subject of theses, of exposes, of novels, of films and more. Conceived by
Jules Verne, Captain Nemo is the master of the submersible boat
Nautilus, which rules the world beneath the waves. His
nationality is unknown. His
wealth is staggering, for apparently it was enough to construct the
Nautilus, a massive vessel completely stuffed with newly-invented and secret
technology, under such a cloak of deception that no-one in the Surface World is any the wiser.
He is shown to be a warrior, when attacking vessels which seek to plunder and destroy his beloved Ocean; he appears as a scholar, trading discourse with his guests. He is an artist of sorts, painting and playing his enormous pipe organ, installed in the Nautilus. Professor Arronax and companions would agree that he has at least partly the soul of a poet for his descriptions and convincing exhortations, which lead them to join him on adventures both dangerous and wonderful.
Although Verne does not divulge the fate of his noble Captain after the events of 20,000 Leagues Under the Sea, there have been various interpretations (including, I am sorry to say, some by Hollywood) which have him turn up some years later. The Nautilus is beached, and the Captain alone, on a deserted island. However, as to what actually happened, I suspect we will need to conquer the depths fully before we can answer that question...
Update: Thanks Ouroboros! I hadn't realized Mysterious Island was, in fact, canonical Verne. I love E2; learn something new every node...heh.