Ygritte: "Swords in the darkness." Aye. The black brothers of the Night's Watch are that at least, as too many of the Free Folk know.
You southerners are strange. A man murders and you train him to kill better. A man thieves or rapes and you send him where it's dark and private. Well, at least you make him promise to be good and then you make him regret even that.
From the time he's woken to the time he's allowed to sleep, he walks the frozen wall, carries frozen stones or boils frozen food. When he lies down at night, he can't have anybody to warm his frozen bed.
Well, not unless the crows like to "nest" together.
We Free Folk have our stories, too. About how one of your king crows found something cold in the woods with bright blue eyes. How he brought her home, through your wall, and declared himself "Night's King".
For thirteen years, he and his queen ruled over his brothers, making sacrifices as black as their cloaks. Lucky for you southerners, the Free Folk rallied to a King-Beyond-the-Wall, as we will when need be, and marched on the ancient castle he had taken as his own, the Nightfort. With the help of the Starks, we killed the demon and cleansed your precious watch. An' then they thanked us, an' kicked us back across the wall. As you always have.