Beneath a withered tree accursed by time and mangled by frigid winds, from arid ground littered by decaying bones, grew a ghastly sprout. Blacker than a blind man's night, its thorny stemlet fed on the pride, rage and suffering that still permeated the barren earth of this derelict world. Akin to a worm, it slithered betwixt weathered skulls and burgeoned, generously fertilized by the lingering wickedness of the dead that once wasted their very own realm. Yet as its branches shrouded the murky skies, as every last drop of sentient pain has been drained from the earth, the hunger only grew. Driven by yearning, it pierced into the Mists and moved on, searching for new feeding grounds, while sowing seeds of irresistible destruction along the way.
The echos of countless lives have been absorbed by its ravenous roots and it learned eagerly about its sentient fodder - our patterns, habits, strengths, weaknesses and most importantly, our desires. It learned to adapt to every person's vice, to present itself in many shapes that could elicit lust, pride, greed, and any other sweet sin that its targets were susceptible to. Little by little, it spread through the worlds, enabling their slow and delicious demise at the hands of their own inhabitants. Though it was convenient to label it evil, it was naught more than a manifestation of sentient turpitude that has been condensed into a single entity - one that people across many realms happily embraced, as it spoke to their dearest, darkest impulses.
World after world, it feasted upon the living and hastened their descent into ruin, yet never before has it encountered one as mouthwatering as Tyria. The history, the magic, the gods, the races that inhabited this realm, the wars they fought and the destructive power they wielded, it was all so succulent and alluring. Hungry for a taste, the thorny tendrils extended through the Mists and slithered into the world unnoticed, like serpents in high grass. For centuries, they skulked and scouted as empires rose and crumbled, as continents sunk into seas and arable lands parched into deserts, until the Dark concluded at last: this was the place where it would sow its main seed.
Tyria was a fecund soil for its philosophy to germinate and blossom. While other worlds were oft quite luscious to destroy and devour, this one was even more enticing - it had the potential to become a lucrative investment. The Dark had learned, from the very beings it absorbed, that its esurient ways were not sustainable and though it could go on for eons marauding life from realm to realm, one day it would have had its last meal and then it too would disappear. Since its inception, it has behaved like a nomadic barbarian on a bloody rampage, but it knew now that it instead must farm our vice and sin; instead of victims, it should make of us its precious cattle.
So the Dark tore its roots from the lifeless earth that gave it birth, for there was nothing left there anymore - its home was barren and a new one beckoned it with sins most ripe. The endless strands of darkness pulled the core across the Mists, lugging it to the ultimate destination. It could almost taste Tyria on the tips of its talons - such a rich and fragrant world, only moments away, just one last pull and...