The world was a wall.

The Barrier Ridge was what they called it. In Tynisa’s College lectures she had seen it marked on maps as delineating the northernmost edge of the comfortable, known territories referred to as the Lowlands. Those maps, set down by Apt cartographers, had been hard for her to follow, and the concept of the Ridge harder still. How could there be a cliff so great as the teachers claimed, and no sea? How was it that the Lowlands just stopped, and everything north from there was… elsewhere? The Highlands, by logical comparison: the mysterious Commonweal which had, for a fistful of centuries, rebuffed every attempt by the Lowlanders to make contact diplomatic, academic or mercantile. Everyone knew that, just as everyone knew so many things which, when looked at closely enough, were never entirely true.

On those maps, the Ridge had been a pair of long shallow curves with regimented lines drawn between them, like a stylized mouth with straight and even teeth. The imagination had been given nothing otherwise to go on, and year after year of students had left the College with the inbuilt idea that the world, or such of it as was worth learning about, somehow came to its northern limit by way of a cartographer’s convention. Now she looked up and up, seeing the heavens cut in two. To the south was a sky swirling with grey cloud. To the north, ridged and corrugated, rose a great, rough rock face that had weathered the spite of a thousand years and then a thousand more, that had cracked and split and had sloughed off whole fortress-weights of its substance in places, but which remained the barrier keeping the Lowlands and the Commonweal apart. Only the greatest of climbers could have attempted scaling it. Only a strong and confident flier would trust his Art to take him over it, penetrating the foul weather that traditionally boiled and clawed over the land’s division.