God Slaying Machine

A long time ago, before the human race itself even existed, planet earth was filled with many different species and creatures. Most of them were strong, and they lived for battle.
The strongest species were named Wigwelaa. Their hunger was neverending. They searched for worthy enemies since the gods created them, but they never found an enemy that was strong enough... except for nature.
Unstoppable fire slowly swallowing the entire place they lived at, storms that had no end, and many other things made life difficult to handle. And although Wigwelaa couldn't die of starvation nor such petty thing as bad weather, they fed on fighting, but since many other creatures around them started dying off completely, soon enough there was no longer a soul that Wigwelaa could fight against.
So, they started fighting each other. They divided themselves into many clans, and started a war so they could survive, not realizing that there were only two ways for them to die, and one of them was dying in battle.
So they fought and fought, until only two clans were left; Yeldiwaang and Yeldael. They no longer cared about reproducing. Since the last daughter was born to Yeldiwaang, no other child has ever been carried by any of these human looking-like creatures. But the light-green haired girl that was born to a Yeldiwaang mother had strength no one's seen before. Soon she killed both clans without even blinking. And thus she wandered through the world, but her freedom did not last forever...