Just outside the Arena of Chaos, there are huge plains that stretch for miles in every direction. Here is the perfect place for mass battles. Here you can practice on your own and even use the Arena's Darkness creator machine to have practise battles on your own. Another thing about these plains. It has a special power to whatever the arena management chooses. So, things like forts and rivers and other things like that can be placed on the plains to create a more tactical battle.