The North is the wasteland
In The Roar, the Northerners within the Wall live with the knowledge that the rest of the world is a toxic wasteland. In this sequel, the truth is revealed that the world outside the wall is flourishing and occupied by the rich in the South. The Northerners were secluded by the rich to preserve nature hence the propaganda of the animal plague. The people in the North live in destitute situations but were content as they thought they were the safest of all. However, the southern civilization is living in fertile lands while the North suffers from diseases and experiences floods.
Children are the reliable ones
The truth about the wall and the plague threaten the eruption of a conflict between the two governments. The adults in the North are livid upon the revelation and only want vengeance against the southern government. The antagonist Mal Gorman intends to weaponizes the mutant children and retaliate with a war. The southerners are also well equipped to retaliate with much more advanced artilleries. Ironically the children are the civil ones as they hope to diffuse the escalating hostilities. Their judgment is not clouded by anger and much more rational than the adults.
The irony of the extermination
Both governments want to defend their cause with the North adamant to keep the poor on the Northern side. The leader of their government is willing to poison the masses to prevent them from ruining their way of life. The lie behind the wall that had been held was the world became a toxic wasteland after a cloud of poisonous gas. Ironically, they intend to inflict the Northerners with poisonous gas when they have lived their whole lives avoiding the fabricated poisoning.
The rich blaming the poor
The people of the South are the rich individuals with the idea of secluding the lower classes in the North to preserve the remaining nature. The plague that almost rendered the world a wasteland stemmed from the corporate greed in the technological revolution. Ironically the South continues to display the same overindulgence while blaming the poor for the fate that had befallen the world. It is ironic that the poor suffer in the North for the faults caused by the greedy upper class.