Dulmis' Sacrifice

At the end of the last Age Those Outside were on the cusp of invading our world once again. We could not fight off their endless hoards forever and Our Lord Dulmis knew this. He enacted a plan he'd been preparing for since his ascension. Our Lord Dulmis destroyed himself along with all of his celestials to shield us from Those Outside.

My blood for your lives
My soul for your protection
My mind eternal

— Supposedly from the lips of Dulmis

He ripped away the power and life from all the immortals he'd help ascend for millennia and used it to craft a shell around our world.

Then he tore himself from the world to power it, and in doing so he undid all that he had changed within the world's spirit. As he left, the land itself split and shifted. Magic ran wild and all things without protection were torn asunder and rearranged to fit the new order of the world.

Aftermath

The only things spared during the sacrifice were the Bastion Cities themselves. They were granted protection so that humanity in all it's forms would be able to survive.

Soon after the world stabilized The Shroud descended. Plunging the world into the current age of isolation.