First draft. Comments welcome but be gentle, this is early sketching.
A long time ago, civilization arose on both the northern and southern continents. Each took somewhat different directions, the northern pushing ahead with innovations in tools and magical techniques, the southern taking a slower, more cautious approach, studying the consequences of each innovation over the course of a generation or more before deciding whether to keep it, build upon it, or roll it back as dangerous. The North and the South traded with each other, Northern metal going into the tools used in Southern agriculture and forestry, Southern grain and wood and such flowing north to feed a culture sometimes too busy to grow its own food, but also running short on viable farmland as they increasingly turned to mining, crafting, and building great cities to house their burgeoning population. Southern growth remained a bit lower, partly due to hesitancy about the ability of their crops to feed their people – nobody wanted to lose a generation to famine because they had too many children – and partly due to a higher death rate, much of the land remaining unconquered and home to predators, diseases and injuries in rural areas taking a higher toll than in the urban North with its healing centers in every city.
And then the inevitable happened. Whether the Northerners dug too deep with their mines, put too much stress on the land with their population, overreached with their magic, or a combination of all of these and other factors really doesn’t matter. In a single day and night, the Great Convulsion tore the northern continent from top to bottom and side to side. The gleaming cities tumbled into wreckage. The mines collapsed. Those on the coastlines grabbed anything resembling useful goods and hurled themselves into ships, boats, barrels, and anything else that might float in faint hopes of survival. The tsunamis resulting from coastal land fracturing, dropping entire cliffsides into the sea, swamped and drowned many, smashed others against nearby islands, and sent some too far out into the ocean to make landfall before their hastily gathered supplies ran out.
The survivors who made it to the southern continent found somewhat less than a warm welcome. Their tools and magic were regarded with suspicion, with reasonable justification, but people sometimes act unreasonably under such circumstances. In most cases, Northern efforts were closely watched, and carefully regulated, for a few generations. In some cases, specific tools and workings were forbidden, due to the potential for runaway consequences. In a few regrettable incidents, Northern refugees were stripped of everything, their possessions burned or cast into the ocean, given whatever rags of clothing could be scrounged, and put to work in the fields until authorities arrived to put a halt to what amounted to slavery. The village of Kastre on the far north-western coast was dissolved, its leaders put to hard labor and its people scattered across the kingdom, when it was proven that they had not only destroyed a refugee group’s belongings, but all of their supplies and onboard equipment as well, and set them adrift, naked and starving, on a ship with no means of propulsion or control.
This is not to say that the Southern continent has been a paradise. Far from it; life has been hard there, often frustrating under stiffly conservative governance determined to avoid the North’s fate. Mistakes have been made. Disasters have occurred. Things have gone Out of Balance despite everyone’s best efforts. Most notably to recent history, eight years ago, the Reiver left a swath of destruction across the land. The Central Kingdoms are still recovering.