Porphyrion

Porphyrion is the king of giants and 40 feet tall. He was defeated by Zeus and Hercules. Porphyrion started the war(See below) between the gods and the giants by kidnapping Hera. Porphyrion was awakened in The Lost Hero, and trying to awaken other giants to fight the gods, also a son of Gaia and [[Tartarus]]

The war referred to has had two iterations, the first of which was in ancient Greece and the second, which repeated most of the events of the first, in The Lost Hero.