A scene from “Unfinished Business”

Jace: The realm will soon tear itself apart if men do not remember the oath sworn to King Viserys and to his rightful heir.

Cregan Stark: Starks do not forget their oaths, my prince. But you must know that my gaze is forever torn between north and south. In winter, my duty to the Wall is even more dire than the one I owe to King's Landing. I need my men here.

Jace: Whilst your men guard against wildings and weather, the Hightowers plan to usurp the throne. If my mother is to defend her claim to hold the realm united, she needs an army. War is coming to the whole of the realm, my lord. We cannot wage it without the support of the North.

Cregan Stark: My father brought King Jaehaerys and Queen Alysanne to see the Wall. His Grace stood at this very outlook and watched as their dragons, the greatest power in the world, refused to cross it. Do you think my ancestors built a seven-hundred foot wall of ice to keep out snow and savages?

Jace: What does it keep out?

Cregan Stark: Death.