Life forms that came from the other planets.
They were the strongest life forms on their respective planets, and each of them had the power to wipe out all the remaining living beings in this world.
The name Aristoteles was given by the humans, and they have no such things in the first place. The Aristoteles don’t fight each other, and they just freely fly around killing things.
Several Aristoteles among them contacted mankind learning about this planet’s concept of “knowledge.”
After Type-Saturn, who received orders from their respective planets and sent it to the others, got eliminated, they entered a final war with the human race.

Angel Voice: Notes.