I remember a Web journal or disc extra where Lucas is talking about Darth Sidious/Palpatine and says something along the lines of "he's the Pure Evil. The Sith Lord who's out for power simply for power's sake. It doesn't matter to the story what motivates him, that's not so important. All you know is that his life has brought him to this point where he wants galactic domination."
Lucas creates amazing characters....he just does a piss-poor job in fleshing most of them out and leaves that to the authors of the novels and comics and the writers of the television series.
Hound of UIster wrote:
Grievous still has more character even without the backstory. Maul has nothing. He is just a grunt.
Oh, yeah. Can't argue that. Maul looked great....he was just as deep as a thimble.