First get a friend or partner to go to Castle Wars with you on an empty world. One of you goes to Saradomin's team, and another goes to Zamorak's team. Once the game starts, go to the opposite team's base and get the flag. Note that your partner must not be away from keyboard, or they will exit to the Lobby and you must do it again. You must score once if you want to get a "flag count". After getting 1 flag count, you and your partner can kill each other to pass the time. (Note your partner can get the Castle Wars kill cape in the same game, have your friend or partner kill you at least one more time than you kill them. Alternatively you can get both capes in one game, but your friend or partner will get nothing, as they will have lost the game.