In the Percy Jackson and the Olympians and Heroes of Olympus series, there have been many mortals and monsters that died in the original myths, but were revived. These do not include species of monsters, such as cyclopes or hellhounds, but individual monsters that are one-of-a-kind, such as the Minotaur or Procrustes.
Back in the age of heroes, the Minotaur was born of the union between Pasiphae and the Cretan Bull. King Minos had Daedalus build a Labyrinth that the Minotaur would live in so that it would never escape and wreck havoc. To keep it under control, every year he'd feed it 14 youths as a sacrifice. Theseus volunteered to be sacrificed and he slew the monster. He escaped the Labyrinth with the help of Ariadne's thread.
Now in modern days, Percy kills it by jumping onto the its back, pulling off one of the its horns and stabbing it in the side. Percy kept the horn as a spoil of war, after Grover returned it from the scene of the battle.
Medusa is a daughter of Phorcys and Ceto and was once a priestess of Athena. After Medusa and Poseidon desecrated Athena's virgin temple, Athena cursed Medusa and her sisters. Her hair was turned to snakes and anyone who would look upon her gaze would turn to stone. She was once a beautiful woman before Athena cursed her. Her only company is her statues. She has a child from Poseidon, Chrysaor, who was born from her neck, and another child, Pegasus, who was born from her blood when Perseus beheaded her.
Percy and Co. are lured into Medusa's lair, called Aunty Em's Garden Gnome Emporium, by the smell of food. Annabeth and Grover realized her identity, but Percy stays, realizing too late. He eventually beheads her, just like his namesake, Perseus.
The Chimera has the head of a lion, the body of a goat, and for a tail it had a venomous snake. It could breathe fire and was immensely strong, and had a high intelligence. In ancient myths, the Chimera was killed by Bellerophon on Pegasus when Bellerophon jammed a lead ball into its mouth. The ball melted, killing it with lead poisoning and suffocation.
In The Lightning Thief, Percy, Grover and Annabeth meet an old plump lady and her pet Chihuahua in the St. Louis Arch. When Percy is forced to wait for the second elevator down, along with a few tourists, the fat lady and the Chihuahua transform into their true forms, Echidna and the Chimera. Percy tries to defend himself and the tourists, but is hopelessly outmatched. After being poisoned by the snake-tail, he desparately jumps out of the Arch into the Mississippi river below, where he is healed. Echidna and the Chimera disappear once the mortals show up.
Echidna was half-snake and half-woman with green skin and reptilian eyes and mother of all monsters and wife of typhon. She was killed the 100-eyed giant argus who was sent by Hera.
Percy and company encountered an elderly plump lady and her pet chihuahua at st. louis arch who later take on their true forms echidna and her son chimera attack Percy and annabeth and grover and several tourists and she and son Chimera chase Percy into the mississippi river and run off before Percy could kill and sent to tarturus either of them.
Procrustes was a Son of Poseidon who lived on the sacred road between Athens and Eleusis. He'd invite passerby to sleep in his bed overnight. While they were sleeping he'd strap them up and stretch them if they were short enough, and chop off whatever hung off if they were too tall. He was captured by Theseus who "fit" him into his own bed.
Percy, Grover and Annabeth are chased into Crusty's Water Bed Palace by a gang of mortals in Los Angeles. He captures Annabeth and Grover in one of his magical water beds, trapping them. However, he forgot about Percy, and proceeded to get tricked into lying down on his own water beds by him. Percy then chopped off his head.
These monster birds have sharp bronze beaks and were able to shoot their feathers like arrows. Before Heracles defeated them, they roosted near Lake Stymphalia in Arcadia and were terrorizing the countryside, destroying food and attacking people. They had all been killed by Heracles for his sixth labor using a brass bell and a bow and arrows. Heracles could not enter the forest that the birds dwelled in, so he used the noisemaker given to him by Athena to scare the birds into the air, and then proceeded to shoot them with his bow.
They attacked Camp Half-Blood when the camp's magic borders were weakened. They were later defeated by Camp Half-Blood and their dead bodies were then eaten by the cleaner harpies before any one could claim any spoil of war.
Tantalus was a king of a western Anatolian City. He was a son of Zeus and a nymph named Plouto, making him an immortal, and not a demigod. He stole nectar and ambrosia from the Gods, and in exchange he gave them his son Pelops as food. Only Demeter ate his shoulder, because she was distraught about Persephone. Zeus put Pelops together again and Hephaestus gave him a bronze shoulder. Tantalus was sent to the Fields of Punishment, where he resided in a small pool of water with a fruit tree above him. Whenever he'd try to eat or drink, the water or fruit would draw away from him.
When Thalia's Tree was poisoned, Chiron was replaced by Tantalus as the activities director. He disliked the campers, but had a soft spot for Clarisse (who didn't enjoy it at all). He reinstated the chariot racing, with the pretense that if anyone died, the killer would have no dessert for a week. He still had his curse, but eventually he was able to grab a hamburger when Dionysus lifted the curse. Unfortunately for him, that was the time when he was sent back to the Underworld.
The Hydra was a giant nine-headed snake which is one of the children of Echidna. It was killed by Heracles by ripping off it's immortal head and burring it under an enormous rock and defeating it.
When Percy sent Tyson to look for doughnuts to give him and Annabeth time to talk, Tyson came back with a box of doughnuts. Percy wondered where he got doughnuts in the forest and he shows them a Monster Doughnut shop. Annabeth said that when a chain restaurant is created, a Hydra is born, much like how a Hydra's head will grow into two when one is chopped off.The Hydra was also featured in the film version of The Lightning Thief.
The Nemean Lion is a lion with a tough hide who is a child of Echidna. The death of the Nemean Lion was a task given to Hercules by King Eurystheus. Hercules wrestled it to death, because only its claws could cut its skin. Hercules wore its pelt as his identifiable look.
The Nemean Lion was sent to attack the questers at the National Air and Space Museum. It was hard to defeat because of its invulnerable pelt, but Percy fed it some astronaut food and Bianca and Zoë shot its mouth with arrows. Percy, like Hercules, wore its pelt afterwards.
Percy meets him in the Labyrinth, somewhere in Texas. He cleans out his stables in order to set his friends free, and defeats him by shooting an arrow straight through all three of his hearts.
Antaeus, a son of Poseidon and Gaea, was a wrestler that collected the skulls of his victims to make a temple for his father. He challenged Hercules (who was on his way to the Garden of Hesperides for his 11th Labour) to a wrestling match. When Hercules realized that whenever Antaeus touched the ground he healed himself, due to his mother being Gaea, he raised him up into the air and crushed him into a bear hug.
Percy, Annabeth, and Rachel met Antaeus in an arena filled with human skulls. Percy challenged him, and forced him to promise on the River Styx that if he won, Antaeus would have to set him and his friends free. Annabeth tells him that he is a son of Gaea,and after cutting Antaeus with Riptide had no effect, Percy wrapped a chain around Antaeus, and lifted him in the air, and then stabbed him. However, with Antaeus dead, his promise on the Styx was no longer valid and Luke was ready to kill them had they not found a way to escape.
In mythology, Cancer came to the Hydra's aid sent by Hera. It was defeated and kicked into the stars by Hercules with him only using his bare hands. It is also said that Hercules crushed a giant crab under his foot.
Percy encounters Cancer while on the Princess Andromeda, on the fountain in the middle of the courtyard, in the promenade. Fighting it, Percy defeated the Giant Crab by making the ground slick with water, and then sliding underneath him to stab the Crab in a chink the belly, which was its weak spot. The crab dissolved, leaving behind its empty shell as a spoil of war.
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 gods. 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. Zeus, however, struck Typhon square in the chest with the Master Bolt at point blank range, greatly weakening him. The gods were then able to trap him in Mt. Etna, where his raw power itself causes lava to ignite from the mountain top in the form of a volcano. After the defeat of her most powerful child, Gaea admitted defeat and fell back to sleep and allowed the gods to rule Olympus without interference.
Typhon woke up from under Mt. Saint Helens and walked across the Continental US but was defeated by Poseidon over the Hudson River as Poseidon opened a hole that dropped Typhon into Tartarus.
In mythology the Clazmonian Sow was defeated by Theseus in Crommyon. It destroyed the forests and regions around the city. It is not one of the most well known monsters in the myths.
During the battle of Manhattan the Sow ran and flew rampart, dragging Percy and a statue of Hermes around the city, until it was killed by Percy with the aid of multiple automatons, built by Daedalus.
Medea was the princess of Colchis, the land of the Golden Fleece in the time of the original Jason. Jason was sent on a quest to retrieve it for his city, and her father agreed to grant Jason it, but only if he accomplished impossible and deadly tasks. With the help of Medea's magic, Jason was able to steal the Fleece from the king and escape. Jason agreed to take Medea with him and marry her upon returning to Greece, which he did. But soon afterward he left her for another. Heartbroken, Medea wrought a terrible revenge by poisoning Jason's new wife and murdering her two children from her marriage to Jason. Helios, Medea's grandfather, then sent a flying chariot driven by golden sun dragons to take her away to Athens, where she married King Aegeus. When Theseus came, she was afraid the King would recognize his son, so she tried to poison him, but it was too late. She ran away to Asia and died somehow.
Leo, Jason, and Piper met with Medea in Chicago, where she charmspoke the guys into killing each other. But Piper convinced them not to. Medea unleashed her sun dragons, and while Leo and Jason beat them up, Piper fought Medea. She destroyed Medea's potions, an escaped on Festus with the guys. The shop exploded. The end.
King Midas was rewarded the Gold Touch by Dionysus because he found Silenus, one of Dionysus' friends, who had become lost. He was happy at first, until he discovered that he could not eat or drink anything. He learned from Dionysus the way to reverse it by running water, so he lived on his life. Until he was chosen as a judge of who was the better musician between Apollo and Pan, and he chose Pan, causing Apollo to throw a fit and give Midas donkey ears. His son Lityerses was known as the Reaper of Men.
Midas and Lityerses live in Omaha, Nebraska, in a big mansion. Piper, Leo, Jason, and Festus crash into his yard because Festus is shot down. He reveals that he works for the Giants, and freezes Leo and Piper. Jason battles Lit, and tricks Midas into "helping Lit up", freezing him. Jason summons a storm, causing Midas's victims to be woken up from the rain. Jason abandons Midas and Lit and brings Leo and Piper to safety.
Enceladus joined the Giants in the attack on Mount Olympus. He was created to destroy Athena. He was slain by a spear thrown by Athena and an arrow from Hercules bow at the exact same time centuries ago. In The Lost Hero, he said that the gods threw a mountain on top of him (possibly after he is killed), and is said that he is the cause of volcanic eruptions caused by his pain.
Enceladus captures Tristan McLean, the father of Piper McLean, so that he could use his daughter to lure Leo and Jason to him. He was killed at Mount Diablo by a combined attack from Jason Grace and a lighting bolt from Zeus.
Porphyrion started the first war between the gods and the giants by kidnapping Hera after being shot with an arrow of Eros. 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 (of course) the king, Porphyrion, the Gigantomachy 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, Heracles, and sent Athena to find him.
He is the anti-Zeus, as he said, and as such nearly killed Jason Grace, if not for Hera being freed at the right instant. He rose at the Wolf House, which is the claiming location for the Roman demigods. He fought against Jason but fled after Hera/Juno was freed from her prison to avoid her wrath.
A blind son of Neptune that was given the gift of prophecy. He is able to see the future and uses his gift to aid Gaea. He took up residence in Portland, Oregon, on 913 SW Alder St., behind a parking lot of Food Carts. Percy is known to mention Korean/Brazilian Fusion Tacos: he is mentioning the Boolkogi Korean BBQ cart. Percy makes a gamble with Phineas: they would each drink a vial of Gorgon's Blood, one healing, the other killing. Gaea influences Phineas to drink the wrong one, and Percy moves on to Seattle.
Being the first queen of the Amazons, Gaea brought her back in order to make the Amazons follow her instead of the current queen, Hylla. Otrera challenged Hylla for queendom over the Amazons, a challenge to the death. Hylla defeats her two nights in a row, and since after the second night Thanatos was freed, Otrera could not come back again.
Alcyoneus was the giant who opposed Pluto/Hades. He was created by Hazel Levesque, who had born him of all the metals in the earth. His skin is made of gold, his heart is made of raw diamonds, His armor is of platinum, and replacing blood, oil runs through his veins. Being made of precious stones and metals, his body is covered with them. His homeland is Alaska, the land beyond the gods, and he cannot be killed there. But Hazel and Frank Zhang, with the help of Arion, pull him across the border into Canada, where Frank and Hazel beat him up and behead him.
Polybotes was the giant who was born to fight Neptune/Poseidon. His touch turned water into poison. When he attacked Camp Jupiter with a legion of cyclops and centaurs, he, after gloating and stepping on a Terminus statue, was killed by Percy when he threw the decapitated statue head of Terminus at his face, crushing his skull.