Okay, if you wish to challenge someone for a duel, you post it here.
In essence, you say
"Hey you, I want to fight. You up for it?" or whatever. As for the topic name, "A challenge" or "-user's name-" tends to work fine. You may put up other things if you like as far as names go, it's not that important. So long as you specify your challenger.
Then you wait for them to respond. (If you're the challenged, you NEED to respond to the challenge with a yay or nay. If you don't respond, it's assumed you're declining.)
After that, the Duel Mod (Tonio Asura) will look through it and see if the challenge has been accepted. If it has, he will make your duel topic promptly, and you may begin dueling as soon as it's up.
A challenge needn't be a 'rare' occurence, feel free to challenge people as often as you like, or to cooperatively come to some sort of agreement to fight - maybe not a challenge, but certainly a friendly duel. I'd like to see the Inter-Realm duels used more often, as practice, leisure, or preparation / warm up for an upcoming tournament. Whatever the reason, please duel! ^_^