Prompt: "The Musketeers (or at least one of them- I like Athos) are captured or something and end up in an illegal underground fighting ring. It's very dangerous stuff, with huge amounts of money changing hands and the fighters kept under lock and key by the "Masters" who sponser the fights. The Musketeers who haven't been captured try to keep track of the situation by going to the fights in disguise and following the progress of their comrade, passing medical supplies and food when they are able, but this is too big for them to crack open on their own. Musketeers are worth huge money in this world, and a fight that pits the King's best soldier against the Court of Miracles' best brawler is a huge event. That would be a good time for the Musketeers to break up this whole ring of evildoers and rescue their man, right?"

Prompt link: http://bbcmusketeerskink.dreamwidth.org/774.html?thread=804614#cmt804614

Fill: Breaking His Prison Forth, here - http://archiveofourown.org/works/1370854/chapters/2929927