Swiftfang was angry to say the least, what did he hate? you may ask, he hated RiverClan, he would do anything to hurt them now, the cats there had made fun of him, picked on him, and told him he was nothing, he was leaving, he wanted nothing to do with them, he hated them almost as much as Ashfur hated Squirrelflight ( references!!!) and so, he diced to join BloodClan, or at least try, with the only thing he had that could help him get in being the fact that he knew all of RiverClans secrets.
( disclaimer, I have nothing against anyone who rp's in RiverClan threads, this is just this character's backstory )