I think I can help you. A developer from Yacht Club Games made a post when the Plague Knight DLC was released and there is a way to unlock it without beating the game first.
Be warned...In my opinion, the Plague Knight campaign is more difficult. But here's the info you need...
On the title screen...Hold Y. Press up, up, right, down, left, left. Release Y.
I hope this works for you. Good luck!
02/18/2016 3:56 PM
no no no . that so sad I wented to play as the King kight