Each attempt will trigger a 30 min cooldown which can be lowered by 30 seconds per skillpoint in Duelist.
You may spend 15 energy to change your (visibly stronger equipped) opponent.
Winning 2 or 3 times will give you a Box of Resources or a Weapon Cache, which will be sent to your mailbox.
You will not lose items on defeat in an Arenabattle but you will lose a lot of durability if the battle takes several rounds since your opponent doesn't need to move into close-combat range first to attack you in comparison to zombies.