Because again going through the mines seems like a good plan. (I mean, it's not much different from infiltrating via the sewers like that one time back home so...) He's not a pro at stealth but can manage it, and even better he's good for any fighting if it comes up instead. He can be quiet about it if need be or garner attention and keep everyone busy for others to get past. He comes armed with weapons and several martial arts styles. Etc, etc, etc.

Also, I still have a search request available for any info gathering that may still need to be done for going into the mines or elsewhere.