Earth (BtVS) - Failed Attempt

When the Shadow Men attempted to forge a living weapon to fight the demons that threatened their tribe in ancient Africa, they reached across the dimensions with their magic.

They intended to infuse a girl with the heart and soul of a Pure Demon. They succeeded but their breach in the wall between realities let the Hermpire Ring slip through.

Fortunately, for the denizens of this world the Powers at Be, the supreme beings in charge of this shard of existence, were paying attention on that day. The Ring was swiftly caught and expelled back through the tear.

But not before it managed to pervert and corrupt some of that demonic energy flowing into the human girl.

The First Slayer.