Character fiction is where you can write, and post stories about your battle arena character. You can only post stories about your approved character, and you can't use other people's characters in your story unless you have their permission. Also, don't have the story end up with your character getting vastly powerful. Any unauthorized upgrades will end up with your character getting un-approved, and you getting a warning. Don't think that, "But he got the super special lightning sword of the gods in my fic!" is a good excuse.