On the Isle of Armor is a Dojo run by none other than a trainer known as Mustard. It is here you will meet Kubfu and will ultimately begin your journey to the Tower of Two Fists with it; however, the Dojo has much more to it than that, most noticeably allow players to battle within it. At the Dojo, there is Restricted Sparring which provides specific battles for players to participate in. As the name suggests, however, certain Pokemon are restricted from being used at the Dojo, and various battle conditions will also apply.
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