We judged they was studying up some kind of worse deviltry than ever.

断定，他这是正在策划什么比往常更加恶毒的主意。

Finding and using the incantation from the magic book Grimoire, Faust has to stop the deviltry and return it back to Hell.

寻找并使用魔法书Griomoire上的咒语，Faust必须阻止那些恶魔并将他打回地狱。