User blog comment:SafeBat/What happens after you capture a monster?/@comment-4820236-20120523202922

My theory: I believe that when a monster is captured, The Client keeps it until they no longer need it. When they don't need it, by then it's probably tame, so they either allow the Guild to do what they want with it, like using it for the Arena, or they keep it as a pet, or they allow it to go free.