Oh dear. This was all a false flag. Narnia didn't expect Amy to be left unchallenged.
Either Iruma had his Scala interrupted, and thus failed, this would have led to a rift in the 13 Crowns between Iruma's supporters and Narnia (and Baal). And since the authority of the Crowns is supposed to be absolute, this would have led to a split that would have caused a civil war that would have gotten Baal's goal of destroying the peace of Delkira's council, which is what he wanted.
Or, Iruma would have had support from Mephisto who would have undermined Amy's authority, thus making him believe Narnia's warning, thus giving him unwavering support for Narnia (and Baal) if only because of the "threat" that Iruma possesses. And, thus, make him a new pawn to control, which can also still lead to civil war. And a scapegoat in the case that Amy just so "happens" to kill Iruma.