Typhon (also known as Typhoeus) is the last known and most powerful child of the earth goddess Gaea, and is also known as the "Storm Giant" or "Father of all Monsters." His wife is Echidna and his father is the Protogenoi Tartarus. He is especially hated by Aeolus, because when he is defeated, thousands of Venti are released, thus making the master of the winds's job vastly more difficult. He is the single most powerful foe the Olympians have ever faced.
Thousands of years ago, after the First Olympian War, Gaea was enraged at the defeat of the Titans (her children), and of how they were locked away in Tartarus. She attempted revenge by sending her last and most powerful child, the great monster Typhon, to destroy the Olympians. Typhon alone is the greatest foe the gods ever faced, even mightier than the Titans themselves.
Having never anticipated such a rival, the gods were quickly forced on the defensive and they eventually went into hiding, except for Zeus, who was frozen with fear. Gathering his senses, Zeus struck Typhon square in the chest with the tremendously powerful Master Bolt at point blank range, but Typhon merely shrugged it off. He knocked Zeus out of his chariot and held the poor god in a strong grip. Typhon tore out Zeus's divine tendons, greatly weakening him, and hurled him away. Hermes and Pan met Zeus and formulated a plan. Pan began to play soft music, which calmed Typhon and fell asleep. The gods stole the tendons and attached them to Zeus. Zeus attacked Typhon and severed the monster's fingers with the Master Bolt. Zeus subsequently hurled Mount Etna on top of his foe, successfully trapping him. Ever since, Typhon's raw power itself caused lava to ignite from the mountain's top in the form of a volcano. After the defeat of her most powerful child, Gaea admitted defeat and fell back to sleep, allowing the gods to rule Olympus without interference ever since.
When the Olympian gods moved and followed the center of power of Western Civilization, Typhon was trapped in Mount Saint Helens. Like in Mount Etna, his raw power ignites lava from the mountain top. Though he was successfully imprisoned for thousands of years, his prison could not hold him forever.
When hypothesizing about the identity of the "Bane of Olympus," Chiron suggests it might be Typhon, due to the latter being the most feared monster at Olympus, though Chiron considered it unlikely. It is later revealed to be the Ophiotaurus instead.
Typhon is mentioned by Hephaestus, who understandably advises Percy and Annabeth to stay away from the Storm Giant. Later, during his efforts to kill a gang of telekhines in The Battle of the Labyrinth, Percy was forced to call on almost all of his power to escape Mount Saint Helens. It was this that weakened the seal on Typhon's prison and made the Father of All Monsters stir in his sleep.
Typhon escapes in a catastrophic explosion of Mount Saint Helens. Following his escape, Typhon heads to New York City. Using the Mist, Typhon is able to conceal his true form from the mortals and appears as a freak storm. The gods, or at the very least Artemis, Apollo, Athena, Hermes, Ares, Dionysus, Hephaestus, and Zeus, are unable defeat him as Poseidon was occupied defending his undersea kingdom from Oceanus and Hades, Demeter, and Persephone refused to fight.
Not even Zeus' Master Bolt, the most powerful weapon ever created, is able to stop him, as shown when Percy, through a projection on Olympus, sees that Typhon merely stumbled backwards before continuing his way towards Olympus. Typhon also incapacitates Dionysus and Hephaestus along the way, smashing Dionysus deep into a mountain, and smashing Hephaestus out of the sky with enough force to create a new lake in West Virginia. While the Olympians are busy fending off Typhon, the Titans make their way to Olympus, which is defended by demigods.
Percy prays to his father Poseidon and asks him to leave his kingdom and come to help the Olympians defeat Typhon. His father agrees and reluctantly leaves his kingdom to assist the gods. When Typhon steps into the Hudson River, the call of the ocean is heard and Poseidon rides into battle along with Tyson and his brethren, the Cyclopes, as well as Briares. They chain the monster down, and Poseidon opens a tunnel to Tartarus, casting Typhon down. Once Typhon is defeated, a wave of venti (storm spirits) is born, much to Aeolus' dismay.
Jason Grace, Piper McLean, and Leo Valdez go to Boreas to get help for their quest to save Hera. As the god explains the release of the storm spirits, he shows them a video image of the gods defeating Typhon with Poseidon's help.
Typhon's true appearance is unknown, since in The Last Olympian, he is always seen to be surrounded by thunder clouds. Through the mist, Typhon appears to mortals as a massive freak storm and tornadoes that tear apart everything in their path. To demigods (who are immune or highly resistant to the Mist) he appears as a colossal shadowy figure composed of dark clouds. According to Percy, Typhon was gigantic enough to use the Empire State Building as a baseball bat, and had blisters the size of buildings, clawed hands the size of city blocks, and feet the size of Yankee Stadium.
In Percy Jackson's Greek Gods, Typhon is described as more or less humanoid from the waist up, but his legs were like the bodies of boa constrictors. On each hand, he had a hundred fingers tipped with red-eyed serpent heads. He had massive leathery wings and long matted hair that smelled like volcanic smoke. Typhon is so fearsome that even the Olympian gods themselves all fled from him in terror after first seeing him, except for Zeus (who was paralyzed with fear, but was determined to set a good example for the other gods by engaging the fearsome foe).
If a demigod or mortal looks at him too long, they risk going insane from trying to comprehend what they are looking at. Based on comments, he has some sort of structure to serve as legs, and claw-like hands. Percy also says that he could not identify the monster's face because it changes every second to an even more horrifying monster than the previous one.
Typhon, as Gaea's single most powerful child, has power of apocalyptic proportions, being even stronger and more powerful than any of the Olympians, the Titans, and the giants, making him one of the, if not the most powerful being in all of Greek Mythology. His mere presence was more than enough to intimidate the Olympians themselves. The second time Typhon awoke in The Last Olympian, although the gods didn't fear him anymore, still they weren't even able to significantly slow him down. Even after his first defeat, the legacy of Typhon's power remained on earth in the form of numerous monsters, like the Nemean Lion, the Chimera, Orthus, etc. These tasks were left for demigods to complete.
- Massive Strength: Typhon is incalculably strong, stronger than any individual Olympian, exceeding even those of the Big Three, since even Zeus was unable to break free of Typhon's mighty grasp on him in their first battle in Percy Jackson's Greek Gods. Hence, Typhon is the only known being to have ever defeated Zeus himself, by tearing out the god's divine tendons, which is a terrific feat in and of itself. He effortlessly drove Selene away, causing the craters on the Moon. He razed many cities, sank entire islands, and tore apart whole mountains. In The Last Olympian, Typhon knocked Hephaestus so hard out of the sky, that a new lake was created where Hephaestus fell. He sent Dionysus flying, burying the god hundreds of feet deep into a mine, crushed under many tons of rubble. Typhon was only defeated in Percy Jackson's Greek Gods when Zeus took him by surprise. Typhon was barely awake before Zeus bombarded him with tremendous lightning bolts from his Master Bolt (blinding the monster and slicing off his serpentine fingers) and crushed him under Mount Etna before the monster had a chance to fight back.
- Durability: Typhon is incredibly durable, almost invulnerable to all of the Olympians' attacks, easily absorbing those of Apollo, Artemis, and Ares. Only weapons of tremendous power, such as Zeus' Master Bolt and Poseidon's Trident, could temporarily weaken and slow down the Storm Giant, though even then he is quick to recover.
- Natural Disasters: Typhon could summon violent thunderstorms, hurricanes, volcanic eruptions, and floods. The crushed, imprisoned Typhon sometimes caused Mount Etna to erupt above him, but couldn't free himself for eons. His defeat unleashed a huge wave of storm spirits, as revealed in The Lost Hero.
- Fire-Breath: Typhon could breathe gigantic torrents of fire from his monstrous maw, and managed to burn off Zeus' beard during their battle in Percy Jackson's Greek Gods.
- Poison Generation: Typhon's two hundred serpentine fingers can simultaneously spew vast amounts of venom that instantly poisoned the seas in Percy Jackson's Greek Gods, managing to kill numerous sea creatures and temporarily incapacitate even Poseidon himself.
- Interestingly, in Percy Jackson's Greek Gods, Percy mentions that since most of the Olympian gods fled from Typhon all the way to Egypt in the form of animals, they might have induced Egyptian myths about "gods with animal heads." However, Percy admits that this is unlikely, since Egyptian myths are much older than Greek ones.
- Also in Percy Jackson's Greek Gods, Typhon is also called Typhoeus.