Flying Castles wreaked slow motion havoc upon the flying castle-less neighbors. A period of open warfare and conquest followed where those without Flying Castles fell to those who did. It was an age of darkness and death from above.
The secret no bard uttered and no poet told, was this: these warlords and heroes also wanted to settle down, find peace, and scratch their own subsistence existence from the soil with pointy sticks. What good is the story of Harold the Great who defeated the Dwarves at Holden Pass when Harold brutalized his way through the pass just to get the quality soil beyond?