Kronos

Kronos is the main antagonist of the Percy Jackson and the Olympians franchise. While in terms of backstory and personality, he is the lord of the Titans, Cronos, he has the powers of the personification of time, Khronos.

Origin
Kronos was the youngest child of the sky, Ouranos, but he used a scythe given to him by his mother, Mother Earth, to destroy him and control the universe. He ruled for a long time, but he ate all his children, because he was told one of his children would overthrow him. His wife, Rhea, hid her son, Zeus, and tricked Kronos into eating a rock instead. Many years later, Rhea tricked Kronos into vomiting out his five other children, who joined up with Zeus, who lead them on an attack against the Titans stronghold, Mount Othrys. Zeus used his most powerful weapon, the Master Lightning Bolt, to reduce Kronos to dust, not truly dead. Zeus threw his remains into Taratus, the deepest put on Earth, with the rest of many of the Titans.

History
In The Lightning Thief, Kronos never physically appeared but manipulated two of the books main villains, Luke Castellan and Ares, God of War. Luke, who was ignored by his father Hermes and had to defend himself from monsters for years, was resentful against the Olympians and Kronos easily convinced him to steal Zeus's Master Bolt and Hades's Cap of Invisibility. He intended for Luke to bring them to Taratus for him to use, but Ares caught Luke. Thankfully for the young demi-god, Kronos convinced the War God that Zeus would blame the thievery of his Master Bolt on Poseidon, causing a huge war. Ares was interested and was manipulated into helping. Cronus then had Ares take the Master Bolt and the Cap.

Instead of having Luke take the weapons to him right away, he decided to give it to an ignorant Percy Jackson, son of Poseidon, who had already been blamed for the theft of the Master Bolt by Zeus. Hades also blamed the son of the Sea God for the theft of his symbol of power and was having several of his monsters stalk him. Percy Jackson eventually made it to Camp Half-Blood, the haven for demi-god children, where Luke was, and Cronus decided to have Percy sent on the quest to the Underworld, where he would have the Master Bolt unknowingly, making Hades sure he also had the Cap and that Poseidon was going to try to take over Olympus for himself. He had Luke summon a Hellhound into the boundaries of the camp, which would convince the people at the camp that it wasn't safe anywhere.

Percy was then sent on a quest to the Underworld with his friends Grover Underwood and Annabeth Chase because they thought Hades was the one who stole the Master Bolt. Luke gave Percy winged sneakers, which were cursed so they would pull him into Taratus when they were close enough to it. Halfway through their adventure, Ares gave them a magic backpack, which seemed harmless enough, filled with supplies, but in reality, it hid the Master Bolt inside it and it would only appear when in the Underworld. The plan would've gone perfectly, except Percy didn't want the winged shoes and gave it to his friend Grover. He nearly got pulled into Taratus, but his friends saved Grover from being trapped in the endless pit. Later, after escaping the underworld, Ares tried to take the Bolt from Percy, but the God of War was defeated and gave up the Cap of Darkness. Percy managed to return both symbols of powers, and the Olympians and the half-bloods both realized that Kronos was behind all of these events. Luke then revealed he was a spy and left Camp Half-Blood, leaving the gods and their children to prepare to fight the Titan.

The Sea of Monsters
In this book, Kronos has convinced Luke to gather an army of monsters. The Titan Lord has also been rallying half-bloods to join his troop, with each half-blood that pledges loyalty to him bringing back one piece of his soul from Taratus, with the pieces being stored in a sarcophagus on his battleship, the Andromeda. Kronos has also made Luke poison the tree that protects the border to Camp Half-Blood, which can only be saved using the healing powers of the Golden Fleece. However, Kronos's plan works three ways. If the demi-gods do not get the Fleece, he can have his army of monsters destroy the camp. If they do, he can take it from them and use it to quicken his return from Taratus. If his forces fail to take the Fleece, then the Golden Fleece will heal the tree so much it will bring back the soul of the half-blood Thalia Grace, as her father, Zeus, turned her into a tree when she was killed by monsters on Half-Blood Hill. This would help Kronos because of in the Great Prophecy, it foretold a child of the Big Three (Zeus, Poseidon, Hades) would make a choice that would save or destroy Olympus at age sixteen. It turns out that the last of those happened, as Percy Jackson managed to recover the Fleece and bring to Camp Half-Blood, resurrecting Thalia, although her tree stays with all of it's protective abilities.

The Titan's Curse
Kronos slowly starts regenerating in this book, still not playing much of a direct role. For the most part, his nephew Atlas and Luke Castellan do most of the scheming and fighting and manipulation. His base, Mount Othrys, is rebuilt on Mount Tamalpais. some time before or during this book, he manages to persuade Luke to take the Mark of Achilles, making him unable to be killed or injured except for a small weak spot below his armpit. This is in preparation for when Kronos returns, and controls Luke's body, as he needs a host body before he returns to his full power, but a normal mortal or monster would be killed if they consumed the essence of a Titan. The Titan army suffers a large loss when Atlas once again becomes trapped under the burden of the sky, and on the same night, Thalia becomes an eternally young companion of Artemis, stopping her from aging into a sixteen year old.

The Battle of the Labyrinth
At this point, Kronos's army has become massive, with almost every species of monsters serving him in some form. Before attacking Olympus directly, Kronos wants to destroy Camp Half-Blood, so he sends troops to investigate the famous Labyrinth of Daedalus, which has moved under America, like most other magical Greek locations and creatures. However, it seems impossible to find a way through the Labyrinth, so he redirects his attention on find the creator of the Labyrinth, Daedalus, and collect the string of Ariadane to use to navigate the giant maze. Meanwhile, some telekhines work on rebuilding Luke's sword, Backbiter, into the scythe of Kronos in Mount Helena, Hephaestus's forge. However, Percy Jackson comes to Mount Helena to stop the telekhines for Hephaestus, but he ends up causing the volcano to erupt and destroy the forge, but Kronos's scythe is saved from the destruction. Eventually, his troops find Daedalus's workshop and the inventor gives them the string. They later betray him, but he escapes their wrath. Only a little while later, Kronos's scythe is finished and he only needs one soul to be resurrected into Luke's body. Percy, using an invisibility cap, sneaks into his base and opens his sarcophagus, paralyzed at the sight of Luke's lifeless body in the Titan's sarcophagus. He sees Ethan Nakamura, a demi-god he fought and didn't kill, who pledges loyalty to Kronos, who then awakens in Luke's body, which now has golden eyes instead of blue.

Kronos takes his scythe and taunts Percy, showing off his powers over time, but the half-blood escapes thanks to the resourcefulness of his friends and the fact that the Titan is still getting used to his new body. The Titan Lord sends a huge army of monsters into the Labyrinth to storm Camp Half-Blood, which are either killed, or retreat when the legacy of Pan scares them away. The Titans can no longer use the Labyrinth, has Daedalus killed himself, destroying the Labyrinth with him.

The Last Olympian
In the final book of the Percy Jackson series, Kronos seems to have already won the war. Most of the minor gods, such as Hypnos, Nemesis and Hecate, have joined his side, he has a near endless army of monsters, the most fearsome monster ever, Typhon, has reawakened and is heading towards Olympus (now at the top of the Empire State Building), nearly all the Titans have been freed from Taratus, Hades and Demeter refuse to help the gods, Poseidon and his troops are bust fighting a war underwater and many half-bloods have been killed in action, have deserted the camp or have disappeared. Kronos is sailing the Andromeda into the ports of New York City, prepared to destroy Olympus while all the gods are busy fighting Typhon in the West. Percy Jackson and his friend, Charles Beckendorf, sneak onto the ship and plant bombs in the engine room. However, Kronos has a spy in the camp (ironically, it's Beckendorf's girlfriend, Selena Beauregaurd) and has his monsters catch Beckendorf and Percy. Percy tries to attack Kronos, but the Titan Lord uses his control over time to dodge without any challenge and gives Percy a small cut, although this cuts through his soul. Beckendorf manages to set off the bombs, as the monsters forgot to disarm them, and blows up the ship, killing himself and many monsters, although Kronos survives, along with Percy, who escaped into the ocean.

Kronos later had Hypnos put all of New York City to sleep (excluding monsters, demi-gods, gods and a few special humans due to the limits of his powers), and Kronos combined his powers with Hecate to slow down time around New York City and make anyone else entering force themselves to leave. They sent forces around all sides of New York City, from the water, the tunnels and the bridges (air attack was made impossible thanks to the Winds). The demi-gods of Camp Half-Blood and the Hunters of Artemis helped defend New York City. Kronos later helped at the Williamsburg Bridge, which was being defended by the children of Apollo and Percy Jackson, who had taken the Mark of Achilles so he could defeat Kronos. Kronos had his half-bloods attack Jackson, who outclasses them, but Percy was forced to retreat when his friend Annabeth was stabbed while trying to protect Percy's weak spot (she didn't know it was his weak spot, she just had a feeling). Percy destroyed the bridge to stop the Titan from advancing.

Kronos and his forces retreated when day came and took refuge in Aunty M's Garden Gnome Emporium, the old lair of Medusa before she was killed. He sent his nephew, Prometheus, to negotiate with the half-bloods, but they refused to surrender. Meanwhile, Kronus talked to Ethan Nakamura, who delivered the blow of the knife. He asked if he knew Jackson's weak spot, but Ethan said he didn't and that he just tried to hit somewhere random. The fighting continued the next day, where along with an army of giants, dracaenae and other monsters, the Titan Hyperion and the Clazmonian Sow both attacked, but they were stopped by Percy Jackson. However, while he was distracted by that, Kronos managed to surround the Empire State Building, leading the attack on a golden chariot, but Chiron, his centaur son, and several hundred centaurs rushed in and sent the Titan retreating with his army. This time, they took refuge in the United Nations building, which Kronos was disgusted by the idea of mortals uniting. Before it even turned into nighttime, he sent a Lydian drakon to attack the defenders of Olympus, with all the other monsters following behind it. The drakon did a lot, terrifying the heroes and causing mass destruction. However, the spy, Silena, who felt guilty about helping Kronos, led the Ares cabin into the fight with the drakon (disguised as Clarisse, their counselor), as they had an argument with the rest of the campers and refused to help in the battle. However, she was killed, and then Clarisse came in, and became so filled with rage, that she killed the drakon by herself and began to lead her siblings against the enemy. However, Kronos's army was just to much and the forces of Olympus were pushed in front of the Empire State Building's doors. However, Hades came in with Demeter and her daughter, Persephone, and his half-blood son, Nico di Angelo and changed the tide of the battle, with his forces of the dead equaling the forces of the Titans.

Kronos created a force field that separated the armies of Olympus, the dead and his own forces from the State Building, the portal to Olympus, himself, Ethan Nakamura, Percy Jackson, Thalia Grace, Annabeth Chase and Grover Underwood. Kronos and Ethan entered the portal to Olympus and went on a rampage. They destroyed statues, cut buildings in half and a lot more. He entered the throne room of the Olympians and prepared to destroy them, thus destroying the powers of the gods and everything they created. However, Percy, Grover and Annabeth fought him and tried to stop him (Thalia was crushed under a statue, not dead, but trapped). In the ensuing battle, Ethan decided that Kronos was causing more harm then good and tried to stop him, but was easily killed. Annabeth was injured in the battle, and all Grover could do was keep her out of the way of Percy and Kronos. Annabeth eventually stopped Kronos by reminding Luke of all of his friends and the promises he made to them, which brought him back to his mind. Luke's body started to disintegrate as the Titan Lord began to return to his true form, but Percy gave Luke Annabeth's knife, which he used to stab himself in his weakspot, killing him, and reducing Kronos to dust. While all this was happening, the Titan Krios was defeated and Mount Othyrs was destroyed, thus ending the Titan Lord's return.

Powers and Abilities
Kronos, as the leader of the Titans, is immensely powerful. He is immortal and can only be killed if his entire legacy is destroyed. In the body of Luke Castellan, he cannot even be killed unless he is hit in a small point in his hand. He also wields a scythe that can reap the souls of mortals, which can kill humans and monsters. He has control over time, using it to freeze and slow down time on multiple occasions. He also has immense skills while wielding his scythe. Also, in his true godly form, he can disintegrate mortals just by being in their presence.