Season 3B AU Post Finale but before Season 4.

I don't own Teen Wolf.

Prologue

Long before the Hales became the protectors of Beacon Hills, long before Beacon Hills was even called that, the Nemeton existed. Planted, fostered and grown long before humanity, or the supernatural had an idea of the importance of this place, the Nemeton oversaw all and was the protector. Early shaman and spirit speakers utilized the power of the Nemeton to attract allies, confuse enemies and prepare for war. This was its sole purpose. Its destruction forced it into hibernation. Though still strong, the Nemeton slumbered only able to watch and feel the shifts in power within Beacon Hills. As protector, it remained vigilant in the pursuit of observing the rises and falls within its boundaries.

It used its power to protect and save Jennifer Blake.

When Jennifer sacrificed unwilling individuals for their power, the taint of this dark act began to spread throughout the land, gathering at the focal point of the Nemeton. Slowly the slumbering giant was awakening. With the sacrificial ritual which opened the minds of Scott, Allison, and Stiles to the darkness, the Nemeton was opened to the dark forces that reside within Beacon Hills. When the chaos, strife, and pain that the Nogitsune unleashed upon the town began, the giant awoke, full of energy from more unwilling sacrifices. The Nogitsune fed on the chaos, the Nemeton drank deeply of the blood that ran like torrential rains. The giant was awake again, its goal to protect Beacon Hills remaining but the method changing. To save the territory, it must control the territory.

The once benevolent protector became the twisted tyrant with one simple goal.