Demons.

For millennia they had stood proud atop the pyramid of life. They were powerful and long lived, knowledgeable in almost every aspect, content to see humans as beneath them. Dirty, weak, stupid humans. They paid no mind to their quick minds and watchful eyes, thinking that they would never rise to be anything other than filth.

But humans learned and advanced. Like oncoming fog they crept quietly forward, devouring whatever lay before them. Foolish, he thought now, to ignore the building of an empire. Too late demons noticed the world that human hands had built.

And found it unforgiving.