The Duel Arena was shut down (and torn down!) in the beginning of the year with OSRS Gold some modifications made in November. The increasing number of scams and RMT spammers has begun to make an already-established feature require be changed. But those changes were meant to act as an initial step toward a full replacement. The replacement was designed to be more secure but still allowing players to take part in the battles (and reward) which are a part of good games.
The PvP Arena works as follows simply say that you're looking to fight and the system will manage it. Continue playing and be notified when there's a match available and once confirmed, you'll be transferred to the PvP alternate save world to face another player of similar level of skill.
Since all these PvP fights take place on an alternative server during your participation with them, all your levels and items will be destroyed and you'll be given a basic set of stats and get to pick a combat style that can boost certain stats. You then pick a second combat style different from the first.
After the fights are over and you've earned rank points, you'll be rewarded and reward points if you are able to win a PvP match (1v1 fight or tournament) that the game organizes for you. You will be able , in the future, to arrange tournaments and duels on your own, these won't reward those points.
Following the efforts to reduce RMT and make the experience more enjoyable and more enjoyable, rewards for non-cosmetic items will only be available in PvP enabled areas. You won't be able to attack anything but other players with them either. Some of these rewards aren't tradeable Cheap RuneScape Gold, while you would expect them to be traded. This is designed to reduce the appeal of RMT spammers and scammers looking for things.