Darkness had been imprisoned within the Shadoverse for many years by Captain Grand till being released by a group of cult followers. He appears to be an evil entity, but in reality he does far more good for the city than anyone else in charge. He has a deep hatred for clowns as they have no business being in modern society. When he eventually took control over the city, he had all of them euthanized in one sweep of which he called "The Harlecaust".
His power of darkness is surprisingly under-used, as he prefers traditional methods of defeating his enemies like good old fashion fisticuffs. It's never revealed what his real name is, nor the history behind the "Dr." in his name. But it's implied he has a PHD in agricultural studies.