First comment - I liked how difficult is to win - but I don't understand something. When I accept to go some arena it doesn't say how many opponents I have to beat. That's frustating, but - I'd prefer harder instead easier.
And since we can create how many characters in arena - I don't know if it should be a little... easy - to help you to gear, lvl up and train your own skill instead create a lot of characters. But, afterall, I'm liking a lot.
Another thing: in most of real life duels you own yours opponents weapons and armor (when they die). am I right, ok?!
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Some changes you guys can do to improve it without modify arena concept:
Money log (to know when you lose or gain anything).