The Ros first came to the Isles after the rise of the World Sea preceded by the melting of the Great Ice. The newly powerful Mascaun who had held a small city on a hill well inland, now held a fortress over the greatest harbor for hundreds of miles about. And the Mascaun were not inclined to forgive previous insults and arrogances directed their way by the Ros whose city was now underwater.
So the Ros took ship, and fled for isles far beyond civilized lands.
There they found 'cavemen', brutish, piggish sorts who from overweening pride and laziness could not even agree amongst themselves for collective defense in the face of direct attack by the Ros. These cavemen could not form a subtle and powerful trading net with each other, and instead they relied on the crudest stone tools each small family unit could make for itself. And so the Men of the Caves, hereafter called the Cavi were made slaves of the Ros.
And each ship chose an island for its own, and each captain made himself Clan Chief, and once a year, they met for several weeks on the Royal Island where the King gave out decrees which had to be ratified by a majority of the Chiefs. This was a time of massive trade, great parties, and lots of weddings as well as lawmaking and justice settling.
And thus things went on for hundreds of years with the Rosclan Isles becoming richer and more civilized and insular. But eventually the Old Empires expanded out, and the descendants of the Mascaun, the Masti Empire came to the Isles. So did other powers in competition with the Masti, but the Masti held the edge being closer.
Wars were fought, but the Rosclan, despite their smaller size had the great advantage of defending themselves in their home waters while the galleys of the Masti were several months from home.
==========
In truth, there were two worlds like such. In one world, a bold and charismatic female, the daughter of the King, came forth, and began to support equality of women and men in all things. She pointed out the great value that doubling the warriors armed with bronze swords and crossbow would have against the Masti.
In the other world, the Rosclan took lesson from their enemy, the Masti, and created something closer to chivalry.
And both worlds began their Hundred Years War against the Invaders from the Sea...
How did they turn out?