Porphyrion is the king of the giants in Greek and Roman mythology. He also acts as one of the main antagonists in The Heroes of Olympus series, second only to Gaea herself, his mother.

Gaea uses Hera's power to release Porphyrion from Tartarus, and is trying to awaken other giants to fight the gods. After Jason Grace, Leo Valdez, and Piper McLean arrive at the Wolf House, Hera, still trapped by the power of Gaea, pleads for the heroes to set her free before Porphyrion can be awakened. However, the demigods act too late and Porphyrion awakens, climbing out of a spire of earth. Jason told the others to keep working while he went to try and keep the giant busy.

When Jason approached him, Porphyrion called him an appetizer and asked if he was Hermes or Ares. However, Jason said he was a demigod son of Jupiter, which only made Porphyrion laugh and thank Jupiter as he considered Jason an offering to himself. Jason and Porphyrion then start a boasting match against each other, with Hera interrupting saying Zeus would destroy him just like before. Porphyrion counters however, saying that Zeus could not destroy him and needed the aid of demigods. He also told them what they plan on doing, traveling to the original Mount Olympus in Greece and destroying the gods at their roots, instead of attacking the current Olympus as Kronos had done.

He then turned away from Hera and brought his attention back to Jason and told him he had no chance, as Porphyrion was at his weakest and could still turn Jason into a grease spot. He then called his spear from the earth and summoned Storm Spirits, lycanthropes, and Earthborn to his location. Jason however stood up to him and called on the winds, which Porphyrion actually looked surprised about. Before Porphyrion could react, Jason climbed up his knee and stabbed him in the ear, before calling a bolt of lightning down which blasted Jason away and blackened the side of Porphyrion's face. However, this did not kill him and Porphyrion raised his spear, which started glowing, to kill Jason.

However, Leo and Piper had managed to free Hera at that moment. She was about to release her true form, so Porphyrion shot Jason a look of hatred before slamming his spear into the ground and vanishing into the earth. When Leo asked Hera optimistically if he had melted, Hera says that he could only be killed by a god and demigod working together and that he fled once she was free as he was not at full strength.