It seems like he was mentioned in the book as having one arm or something like that but I can't remember. I'm reading the second book now so i'll have to wait until I get to the third to really get a feel for what is going on.(with Thoros anway)
Ok, that makes sense now, for some reason I pictured that character differently. In the first book, wasn't there a guy who stormed one of the holds with a flaming sword? Was that him?