From Introduction:
Deep under the earth lies the ancient burial grounds of the sacred unicorns of the Southern steppelands. Unlike their swift and graceful cousins to the north, the Southern unicorn was a lumbering behemoth, covered in armour, rippling with brute force. Highly magical in nature, they long ago waged and lost a mighty battle against a succession of evil wizards intent on their undoing. They were finally laid low by the sorcerous tsar of the mighty Po empire, when he brought his invading horse army by ship to the Southern steppes. Rapacious and unrelenting, the tsar was finally himself undone when the queens of Takunga banded together — something that would have been unthinkable a mere generation earlier — and overcame his magic.
But they could not defeat the tsar and his cavalry soon enough to save the unicorns. Even as the last of the Po fled back to the sea or died upon the steppes, the last of the unicorns crawled her way to the sacred burial grounds of her race and expired. These grounds went undiscovered by humans for centuries. Even when they were finally found, they were buried by the gods before they could be looted. Now they lie inside of subterranean caves, awaiting discovery by some brave or foolhardy explorer.