Arkayna, Zarya, Emerald, and Piper--unexpected heroes who together become epic warriors--are drawn together by a prophecy to battle evil.In an effort to get Em out of the house, the Mysticons go to the mall, where Em is swept up in the world of a Battle-Bots style competition, "Machinations." When she and Piper team up and enter the competition, they not only find themselves battling with robots, but against new friends with scorned feelings.