S1·E147 Reversed Future. Thunder Emperor Zeon. Prelude to Ruin

The team is able to overpower Riou. Riou tells his book owner Bankis to come out and fight. Bankis is revealed to have been hiding inside Riou and once out, tells them that the timing to cast spells will be easier now. As Riou overpowers the team, Dufort and Zeno arrive shortly after revealing they have burned Zarchim's book and prepare to battle Riou.