The Aurochs of Leudania

Once, long before even the native tribes of sacred Leudania settled the river valley, a herd of massive wild bulls- aurochs of the forests- roamed the dense greenery. Their presence was a calming touchstone for everyone who made their way into the labyrinthine lands. Lost travelers, hunters, predators and prey alike- the bulls had a serene countenance that somehow brought all into equal standing among them.
Awe and reverence for the beasts kept the peace for a great many ages until a man with a worm in his head raised his blade in the name of a creature long dead but never gone nor forgotten. The aurochs fell to his dagger one by one, some in their own beds, some atop a bloody altar. Even as his evil task went unfinished at his death others took the sins upon themselves and over time hundreds became dozens became a handfull, until finally one remained. Centuries had passed at this point, but no man set eyes on the last beast although the whispers never let them forget this unfinished task. In their deaths the seemingly dumb beasts showed their capacity to tear loose the yoke of fate thrust upon them by a shadow in the very bones of the land and poured all that their kind ever were into the last of the Leudanian Aurochs. A celestial avatar of serenity despite the evils of the world was born and as modernity scraped away at the edges of the great forest, the wild places still held their own as a towering figure appeared and any who sought to delve too deep into the secrets of Leudania were filled with a desire to leave nature be in this sacred realm of the Auroch.
Nothing can last forever, however, as eventually the beast too fell to the tainted blade. Darkness swallowed the once peaceful valley as the Auroch's protection was shattered to allow sinister forces to permeate the land. Travel became nearly impossible and bloodthirsty beasts proweled soon-to-be-abandoned trails. Sacred Leudania was transformed into an insurmountable trial, one that tore at the very mind and soul of the unfortunate wanderers that stumbled across it. Precious few made it back alive, though not always sane, and even more disappeared into the fog-choked wilds to die, or worse. 
And yet, one man brings back a story to the daughter of a rigid academic that ignites a fire in her heart. The desire to find this anomaly within a mystery consumes her in an almost otherworldly way. Absolutely ancient folk stories told over fires on her early days as an anthropologist ring in her memory with the mention of a sole comfort found within the malicious heart of the river valley.
Taller than many trees, appearing almost from nowhere with an air of comfort and serenity, the man describes an encounter with a massive white Auroch.