UnderCorrupt

Prologue

Long ago, two races ruled over the Earth.

HUMANS and MONSTERS.

For a time, everything was peaceful. The two races worked together in harmony, one's physical strength perfectly complimenting the other's Magical strength.

For a time, everything was good.

When it happened, it happened without warning. A crippling blow that shattered the world as they knew it.

The humans knew nothing of it. All they saw was their once-allies had suddenly lashed out, brutally, viciously attacking.

They did not see how only a fraction of the monsters attacked. They did not see how the monsters were at war with their siblings.

They did not see the tainted, corrupt darkness, twisting in the monsters' souls.

All they saw was betrayal.

So they sealed the monsters underground, both the Corrupt and the Pure, never noticing the battle raging between the two.

And the battle became a war, a war of Pure against Corrupt.

For a while, ideas were talked about. A machine to bend space, reverse time, to take everything back to how it was before, and a Core to power such a machine. But as the Corrupt grew stronger, the plans were abandoned and the Royal Scientist had to turn his attention elsewhere: finding a cure, and creating weapons for the War.

Over time, seven children fell into the Underground. 

The first was taken in by the Royal Family. But when the prince was killed, the child's life was taken by the Corrupt, and their Soul used for the strengthening of the Corrupt Army, the king declared that any human to fall must be killed immediately, their Soul to be used to defeat the Corrupt Army.

The queen was disgusted by this. Had it been safe for her to run without fear of becoming one of the Corrupt, there is no doubt she would have done so. As it was, she remained in New Home, teaching the young monsters what life used to be like.

Six more humans fell. Despite the queen's best efforts, they were all killed, their Souls taken to the King.

And then one more human fell.

They were Determined.

No monster truly knows how they did it, but they made it alive and unharmed to Asgore.

They could have killed him.

They didn't.

Instead, they asked him why he would spill pure blood, when that was exactly what the Corrupt did.

The king spared the child, and they spared him.

Fearing that if they broke the Barrier, the Corrupt war would destroy the surface, the king and the child agreed that it would be best if they remained in the Underground until the war was won, won or lost.

They returned to live with the queen.

And the war raged on.

Heroes rose and fell, both to their sides.

Battles and skirmishes were won and lost.

Lives, Pure and Corrupt, were taken. Souls that glowed and Souls that repelled the light were shattered. Dust, white and black, was spread.

And still, the war raged on.

And this, this is where the story begins.

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A/N so I had an idea and now I'm doin' a thing! I hope you enjoy it!

DISCLAIMER:
I do not own Undertale, nor any of its characters (Those belong to the awesome person known as Toby Fox!). The story, though, and the AU, are my own ideas, so I'd appreciate it if you could not claim them as your own.