I see what you're going for, but I think the -10 DEF is too much, even for a Knight. This removes the point of the melee class, as they NEED high def. The concept is great, but the -10 DEF is way too far. I could see this working with perhaps 10-12 def though.
Overall, GREAT concept, but the balancing is not good. Also, the sprite is on the uglier side, mainly due to the extreme contrasts.