|“||I was created to be Zeus’ replacement, born to destroy the lord of the sky. I shall take his throne. I shall take his wife—or, if she will not have me, I will let the earth consume her life force.||”|
–Porphyrion, in The Lost Hero
In ancient times, Titans such as Kronos and Hyperion were defeated by the gods, namely the six children of Kronos (Zeus, Poseidon, Hades, Hestia, Hera, and Demeter) and by their allies. Soon after, however Gaea brought forth the giants, who were solely born to avenge their elder siblings' defeat. By this time, all of the younger Olympians (Zeus' children) had been born, and were preparing the way for the new demigods.
Porphyrion started the first war between the gods and the giants by kidnapping Hera after being shot with an arrow of Cupid. This, of course, made him fall in love with the Queen of the Olympians, so he started the war to keep Hera and to avenge the Titans. Led by Alcyoneus and the king, Porphyrion, the giants attacked Olympus. Warned by the Fates that the Olympians could not defeat the giants without the help of a lion-skinned-mortal, Zeus decided that this must mean his son, Hercules, and sent Athena to find him.
Hercules defeated Alcyoneus after injuring him in the giant's homeland, Pallene (where Alcyoneus was immortal), and then killed him outside of Pallene's borders. Porphyrion later dueled both Zeus and Hercules, but the combination of both god and demigod working together destroyed him, as only a god and demigod working together can defeat a giant.
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 awakened, 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, wolves, 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.
While Alcyoneus is fighting Percy Jackson, Frank Zhang, and Hazel Levesque, he mentions that while Polybotes is preparing to destroy Camp Jupiter, Porphyrion is preparing for the real battle in Greece, where the Gigantes plan to destroy the gods by destroying them at their roots.
When Jason and Percy are comparing notes on Gaea's activities, Jason mentions that Porphyrion was planning on going to Greece and destroy the gods at their roots.
Porphyrion is among the giants assembled in the Athenian Parthenon, where he is seated on a massive makeshift throne, as seen in Piper's dream. He is approached by his daughter Periboia, who inquires as to why they have assembled in the Parthenon, rather than the slopes of the original Mount Olympus. The Giant King harshly responds by claiming that the mountain is currently a barren peak that offers them no glory, while the Athenian Parthenon holds the Olympians' memory best, with it being the most powerful symbol of the Olympians in the minds of mortals. Porphyrion claims that when the "blood of Olympus" is spilled there, the Acropolis shall be razed, with the hill crumbling and all of Athens being consumed by an awakened Gaea. Unlike her uncles, however, Periboia isn't convinced, and tries to dissuade her father from unwisely tempting fate, reminding him of the Seven Heroes of Olympus also having friends in Athens. At Porphyrion's request, Periboia's uncle Enceladus tells her about Delphi being taken back from Apollo (which closed off the future to the Olympians), and introduces his brother Thoon, the bane of the Fates.
Enceladus was able to predict that it would be Percy and Annabeth leading the rest of the Seven in an assault against the giants. Hence, when the Seven Heroes of Olympus finally make it to Athens, Porphyrion's daughter Periboia is the one to capture Annabeth, while Enceladus takes hold of Percy. When Periboia offers to spill "the blood of Olympus," Porphyrion insists that it must be done by his brother Thoon instead. With some help from Piper, Percy manages to escape, with Annabeth in tow. Percy manages to temporarily knock Porphyrion down by holding his spear to the ground as the latter charges, but the Giant King is quick to rise to his feet again. But, just as things were beginning to look hopeless for the Seven, the healed Olympians arrived at that moment, just in time.
Porphyrion faces off against the combined might of Jason and Zeus, and is ultimately knocked off the cliff of the Acropolis by an extremely powerful gust of wind from the demigod and destroyed by a blast from Zeus' Master Bolt, which reduces the Giant King to ash that spreads across the landscape, to prevent Gaea from raising her son once more.
As seen in The Lost Hero, Porphyrion is very self-confident and arrogant. Even in his weakest form after waking up, he felt no threat from Jason, Piper, and Leo. He even went so far as to joke with Jason, by saying that they would start their fight by boasting when Jason tried to sound intimidating. Even during their fight, he does not seem at all afraid of Jason or make any attempt to stop Leo and Piper from trying to set Hera free. Even when Jason manages to hurt him, he only becomes angry.
While Porphyrion is intelligent, this is sometimes is hindered by his overly self-confident and arrogant aspects. He commented on how the giants were much more patient than the Titans (namely Kronos), and that he knew how to permanently kill the gods, by destroying their origins in Greece. Porphyrion also knows when to cut his losses, as once Hera was free, he knew it was time to escape, showing a cautious side and knowledge of his own limits, despite his self-confidence.
In The Blood of Olympus, Porphyrion is shown to be a harsh and controlling father to his daughter Periboia. He is also a staunch traditionalist, and would only have Thoon spill Percy and Annabeth's blood.
Porphyrion is taller and stronger than any of his giant brethren when he is first awakened, and he "towers over them" while standing in their midst in The Blood of Olympus. Jason also comments that Porphyrion was so large, muscular, and dense that it was like he had his own gravitational field, being at least forty feet tall in his weakest form. Porphyrion is humanoid from the waist up and, like his brother Enceladus, has his own set of bronze armor. He also has green dragon legs like the other giants, which are the color of lima beans. He has green hair which is the same color as summer leaves, which are braided in long locks and decorated with quite a few weapons. The weapons include daggers, axes, and full-size swords, some of which were covered in blood or bent, possible trophies taken from defeated demigods. His eyes are completely white and are described as looking like polished marble, "as white as the Mist". In battle, Porphyrion wields a huge spear, which he can will to glow with power.
- Prowess in Battle: Even for a Gigante, Porphyrion has enhanced strength (enough to effortlessly backhand Percy Jackson "like a pesky fly"), and could more than likely be equal in power to Zeus. In the first Gigantomachy, he was able to fight mighty Zeus himself on apparently equal footing, though he was eventually defeated, with Hercules' help. Later, in The Lost Hero, even after seeing his weakened form, which he describes as being “scarier and more ripped than Enceladus," Jason Grace (one of the most powerful demigods in the world and an outstanding fighter) feels sure that no demigod can defeat him alone. However, in The Blood of Olympus, Porphyrion at full power is finally defeated by the combined effort of Jason and Zeus working together.
- Electrical Resistance: Porphyrion has a strong resistance to electricity, as even when struck by Jason's lightning directly in the ear, he was uninjured, as it only angered him and blackened his face. However, Porphyrion is still vulnerable to electricity from the tremendously powerful Master Bolt, since Zeus used it to severely weaken and ultimately kill him in The Blood of Olympus.
- Giant Invincibility: As a giant, Porphyrion can only be killed by a god and demigod together. His armor and skin are regenerative and will heal during battle at an accelerated rate. Hence, he was brought down by the combined efforts of Zeus and Hercules, and the second time around by the combined efforts of Zeus and Jason.
- Unknown Ability: During his fight with Jason in The Lost Hero, Porphyrion made his spear glow, but it is unknown what effect this has. He only states that he knew exactly how to kill Jason as he knew how to kill his father. Oddly, he didn't seem to use it while fighting Zeus in The Blood of Olympus.
- Reflexes: Despite his size, Porphyrion has incredible reflexes, enough to deflect a lighting bolt from Jason with his spear in The Blood of Olympus.
- In mythology, Porphyrion kidnapped Hera in order to start a war with the gods.
- He also seems to carry a liking for her in the book he first appears in.
- Much like how Zeus and Kronos were the youngest children of their fathers, but became king of their pantheons, Porphyrion is said to be the youngest of the giants and is their king.
- Porphyrion is the only giant encountered by the heroes so far that survived the first encounter, as Jason and Zeus killed Enceladus, Frank and Hazel lured Alcyoneus out of Alaska and killed him, Percy and Terminus killed Polybotes, and Percy, Jason, and Bacchus killed Ephialtes and Otis, while Damasen willingly sacrificed his life to save Percy and Annabeth.