The Ledge: Third Breach
The Great Synthesis
When he was ready, Devidian commenced the Great Synthesis. He disappeared from the Prime World and forged a demiplane from the very stuff of chaos. It began as a vast blue void with a spindle of rock through the middle. Although it was created in the planes of chaos, the demiplane was connected to the Prime World by a conduit of magic. Devidian used this lifeline to leech elemental power from his old home, amassing the raw materials he would use to build The Ledge.
The archmage shaped a vast slab of rock into the Ledge as it exists today, hanging from the infinite cliff and surrounded by void on all sides. He bound a legion of elemental spirits to his cause and commanded them to work until his world could support life; they made a sun from fire, breathed air into the void, and carved rivers, lakes and seas that they filled with pure water. They raised hills and mountains, dug valleys and dragged rich soil from the prime world.
Ailing nature spirits from the prime world learned of his creation and flocked there to plant trees and later, to stock the wilderness with animals. When it was finally ready, Devidian gathered together thousands of uncorrupted folk from the corrupt planet and transported them to their new home.
There has never been an adequate theory to explain how Devidian did this, although divine intervention seems likely, especially given the way The Ten Companions became Conduits. All that is certain is that Devidian was missing for decades, leaving his companions behind to protect their people. He returned only just as war finally reached the shores of the island sanctuary. Devidian and a few thousand abandoned Golarion en masse, leaving the world to its inevitable collapse. Tales told in the darkest, drunkest watering holes claim that this migration was rushed and Devidian had not finished the wards that guarded his demiplane from the maelstrom without.