As the war dragged on, there arose a shortage of young soldiers, most having died in battles or from other, more subtle dangers of war such as hunger and disease. So the Emperors turned to their wizards. The wizards at first actually fought the battles, but then decided that it would be more convenient if they were to simply summon hordes of monsters. Such monsters were effective against the general populations and armies, but not against the enemy wizards who could defend themselves with magic. Those wizards who sought assistance from the powers of Chaos to summon monsters from the Planes of Chaos became known as twisted summoners. They particularly worshipped Bhael, Lord of Monsters and Fear.
Then in BY 1560, the summoning stopped as if something was blocking the passage of the monsters into Kaelaross. With great concerted effort the wizards brought the blockage along the passage and into Kaelaross. The blockage was the chaotic god Bhael, and the wizards had just summoned his avatar.
All of the wizards who had participated in his summoning died instantly heart attacks and strokes as a massive wave of evil magic hit them and surged through their weakened bodies. For twenty days and twenty nights he stalked the land, teleporting from city to city and from continent to continent, slaying indiscriminately, creating many monsters and destroying features both man-made and natural. No mortal who saw his face survived the horrifying shock they received; all died of fright.
It took the personal appearance of two Gods of Law, Rhondus and Adonor, to apprehend and banish Bhael. The battle took three whole weeks, and like Bhael's initial rampage, the combatants teleported across the surface of Kaelaross, seeking some tactical advantage that mortals could not understand. The battle was so violent and powerful that land masses were raised, lowered, shifted around, split up and amalgamated. The whole physical geography of Kaelaross was deformed, in some parts out of recognition.
The four empires had collapsed into anarchy as monsters roamed, raided and multiplied. Humanity was now on a collision course with extinction as farmlands were now seas and cities had been thrown up into mountain ranges. Humanity had fallen from a war against itself into a fight for survival against the unhuman hordes of chaos formed by Bhael and their own wizards.
It was only through the work of the priests of Law that humanity managed to pull itself back from the brink of oblivion and the maw of Chaos. With guidance from the Gods of Law, humans, halflings, elves and dwarves began to rebuild their world. The four empires had collapsed and split into regions that were now on their own.
The year is now BY 1610 and fifty years have passed since Bhael's banishment. Things have begun to stabilise. Out of the untamed wild lands where monsters roam, the brave and the strong are carving out their own dominions, while bands of terrible monsters still prey on the weak and foolish.
New kingoms are forming, possibly the start of a new generation of empires. However, the priests of Chelmor and Rhondus have been charged with keeping detailed and truthful accounts of the Wizard Wars and the Coming of Bhael. Wizards are a lot less popular and accepted than before the war, though some have proved their worth.
This is in many ways a new dark age. Life is often too short, and ignorance is widespread. Towns lie in ruin and much of the wealth is in the lairs of fell beasts.