In order to finish the world, a great source of energy had to be created - the sun. The sun is the key to the cycles in the Aztec creation story. As the sun is so powerful, it can't just be created. It must only exist through the sacrifice of a god. The god chosen was Tezcatlipoca.
Tezcatlipoca only managed to generate half a sun, resulting, in making this first creation incomplete. During the first age, the deities created giants from ashes, and gave them acorns to eat.
A fight commenced, between Quetzalcoatl and Tezcatlipoca. Eventually, the sun was knocked out of the sky, and in anger Tezcatlipoca sent jaguars to destroy the giants.