It seems like everyone has decided that Havik is Skab's real name. I disagree though. Havik is apparently an ally of Darius, who although is listed as neutral, seems to be a hero vigalante type in his realm. Could you see Skab as being his partner?

I think it's safe to say, based on that alone, that Onaga is Skab, and we haven't seen Havik yet. I also think that the sub-boss is neither named Havik nor Onaga, and has yet to be revealed to us.