What the hell was he? By killing him all of a sudden, (wasted opportunity), we never got a chance to see what he was. Did I miss something? Was he a man? A mutated monster? A demon servant of the witch? They blew a chance to have a good fight scene with him.
It was not human, as you could clearly see when it was killed by the explosion. It didn't burn up like a human body would, it just disintegrated. Most likely created by witchcraft.
Yeah, I think it was just a suit of armor magically powered by the witch. Considering she could turn into a dragon, I'm sure she could manipulate armor to move around as if a huge man was wearing it.
That said, it was kind of a waste that he just gets "killed" in a random explosion, rather than being taken down by one of the ronin. But I guess they needed to spend more money/time on animating the dragon fight.