Arenas from #11 to #16 are Legendary Arenas. Once you move into them, you are eligible for Season Rewards. Earn Skill Rating during a month-long season to unlock a reward pack that you will claim at the end of the Season. You must finish the season with Skill Rating of 6000 or above in order to be eligible for Season Rewards. The content of your reward is based on the highest Skill Rating you achieved during the season. If you drop below the 6000 mark at any point, your highest Skill Rating will be reset and your reward will be based on your new highest Skill Rating after passing the 6000 mark again.