If you can just be more honest and tell us it's YOU who's having a problem unlocking crowler, then I would have gladly helped you. Since you're so bent with preserving your image and reputation which doesn't even matter in this site where there's anonymity, I have to pass up on your question so you can learn one bit.
Since this "community" is so bent with critisizing others, I wouldn't admit anything to be honest.
To sorrel, I don't know which are the missions for unlocking him. But it's usually just playing around. For comeback victory, just use a pvp or beater deck, get some damage and then win