Arenas: The Match Seeker is expected to provide an Arena for battle; however, they may forfeit this right to the opponent in exchange for posting second. Arenas have the most far-reaching consequences for a match and can have any attribute the designer wishes, including structural move restrictions. It is assumed that when a Challenger accepts a Seeker's challenge, they agree to the Arena and any of its inherent traits/restrictions/effects. Arenas can be simple or complex.
From the Battle Tower thread. If it means that much, I'll post first.