Luke Castellan

"Ethan. Me. All the unclaimed. Don't let it...Don't let it happen again."

- Luke making his final request to Percy

Luke Castellan is a Greek demigod, the son of Hermes and the mortal May Castellan. He was one of the main antagonists of the Percy Jackson and the Olympians series. He was tricked by the Titan Kronos into hosting his spirit. Although he is considered as the series' main human antagonist, he died at age twenty three as the hero of the Great Prophecy. He is portrayed by Jake Abel in The Lightning Thief. Abel reprises his role in The Sea of Monsters while Samuel Braun has been cast to play a young Luke in the film.

Early life
Luke was a son of Hermes and May Castellan, a female mortal who can see through the Mist. When he was nine years old, Luke ran away from his mother's home in Westport, Connecticut because of her unstable mental problems brought about by the curse of Hades, which was placed upon the Oracle, who she had tried to host. He traveled for years alone, making mortal and demigod friendships that never lasted long, while only having a golf club for a weapon, as his Celestial Bronze sword was melted in acid by a monster.

When he was fourteen Luke found Thalia Grace in a dragon's cave near Los Angeles after she had followed Zeus' sacred goat, Amaltheia, there. Together, they had traveled across the United States, battling monsters, fending for themselves, until, one morning, they had reached Richmond, Virginia, where once again, Thalia was in pursuit of Amaltheia. Luke seemed to have a crush on Thalia and just couldn't tell her no, even though he knew it was against his better judgement. The goat directed them to an old mansion and once inside (Luke's handiwork) they discovered it was a deadly trap. They met Halcyon Green, a demigod son of Apollo, who had been imprisoned inside the mansion, unable to speak, because he had saved a girl's life in his youth, with his abilities to see into the future, incurring the wrath of the gods. A part of Hal's curse was also to bring in demigods to be eaten by three leucrotae who feed at sunset. Luke was angered that the gods would do this to Hal and wanted to find a way to rescue him and Thalia. Hal told them that every demigod thought that at first, that they could escape, but soon realized it wasn't possible. Hal told them of a treasure that was in the mansion, assuming they came there for it, but they hadn't. They went after it anyways. Luke was magically able to break the lock, and Thalia was able to claim the Aegis bracelet as a sign from Zeus as he had a shield very similar.

They were running out of time and ways of defeating the leucrotae until Luke discovered they could make Greek Fire, after hours of searching the Internet with no solution. Within the hour, they had created the Greek Fire from different ingredients and some lightning. Hal decided that he would sacrifice himself to give them time to escape, as he may have foreseen. But before he did, Hal had predicted Luke's dark future but left him vague answers when questioned about it. Luke didn't know what he meant, but was disturbed from what he said. Hal also gave Luke his personal diary and a dagger and made Luke promise that he would learn from his mistakes and not be pushed around by the gods. Thus, by making this promise, Luke made the first step towards his ultimate betrayal of the gods and allegiance to the Titans.

When the Leucrotae attacked, Hal used the Greek Fire to cause an explosion, which killed himself and two of the monsters. One leucrota escaped, but barely, which surprised Luke, but Thalia was able to use the bracelet to summon Aegis and scare the monster away, giving them enough to reach the doors, just as the mansion completely exploded. They got away quickly, cleaning up in the local restrooms, and resting before Luke sensed a presence in a nearby alley.

It was in that alley, the two met Annabeth Chase, and, adopting her as his sister, he became the fatherly figure of the group, they left Richmond and headed to their safe house on the James River. They fought for survival and avoided monsters together. When Thalia got injured by a monster and Luke and Annabeth wanted to rest, Luke took them to his mother's house to heal their wounds. When they approached the house, a loud voice boomed above "You shouldn't have returned", but that didn't seem to matter to Luke. There, Luke met Hermes, his father, for the first and only time. Luke was angry with his father, and demanded to know why Hermes had never showed up when Luke prayed to him so desperately, as he hid from his mother when she had fits, and when they were on their quest. Hermes inadvertently revealed that he knew Luke's fate, and when Luke eagerly asked about it (since Halcyon had only given him vague answers), but Hermes refused to tell him, knowing he had said too much. Luke then told his father that he couldn't possibly love him if he wouldn't tell him, and left with Thalia and Annabeth angrily.

According to Thalia, Luke began to act like he had something to prove after that moment. They got into more skirmishes because of his recklessness, fighting more monsters, and  they ran into the Hunters. They asked Thalia to join, and she refused, saying she couldn't leave Luke. Zoë Nightshade, Artemis' lieutenant ( at the time), hauntingly told her that Luke would let her down (which would later come true) and that caused Thalia to resent and dislike the Hunters, as she did not believe them.

Eventually, a saytr named Grover Underwood found them. Together, the quartet began to travel to Camp Half-Blood but were chased by monsters sent by Hades, because he was mad that Zeus had broken their pact of the Big Three, by siring Thalia. Upon reaching the Camp Half-Blood border, Hal's first prediction came true, as Thalia chose to sacrifice herself so that Luke, Grover, and Annabeth could get into camp without being killed by the monsters that were hot on their trail. As Thalia was dying, being surrounded by monsters, Zeus took pity on her and turned her into a pine tree. From that point on, Luke lived at camp all year round, all the while slowly falling into darkness, angry at the gods.

Allegiance to Kronos
When he was about seventeen, Luke was offered a quest by his father Hermes: to seek a Golden Apple at the Garden of Hesperides from the tree. He was honored by this offer, but eventually began to question it, as it was done before by Hercules, and he didn't want to do a quest someone had already done. He went on this journey, but failed and was scratched (and given the scar on his face) by the dragon guarding the tree, Ladon. He returned to the camp and according to his words, was treated with "pity" by the campers. It was then that he began to hold a grudge against Olympus and his father, Hermes, who he felt didn't love him. He wanted to tear Olympus down, stone by stone at that point. Luke apparently was able to injure Ladon and steal a claw; he has since kept the Ladon's claw in the Big House attic. He bided his time of revenge and began to dream of Kronos.

He was later contacted in his sleep by Kronos, Lord of the Titans. The nature of this encounter is unknown, but he was convinced to join Kronos' cause out of a desire for revenge. He was assigned to steal the Master Bolt, Zeus' primary weapon, and the Helm of Darkness, Hades' godly weapon, in order to start a war between the gods.

On a camp field trip to Mount Olympus he made his move. While the other campers and counselors were asleep he entered the throne room and was able to steal the Master Bolt and the Helm of Darkness. The gods believed that no one would ever dare steal their symbols of power, so they left them by their thrones. They later discovered the theft and went to search for the thief. The Furies went to work searching for Hades, while Zeus sent out his best trackers, Artemis, Ares and Athena. Ares found Luke and fought with him to get the bolt back. According to Luke, he would have won, but underestimated his opponent and was outmatched. However, he managed to save himself by speaking in Kronos' words that if the Master Bolt was successfully stolen, there would be a full-scale war. Ares was awed by this, as he was the god of war, and spared Luke, but took the Bolt and the Helm with him. It is presumable that Ares was dreaming of Kronos, although unknown from before or after Luke's conversation with him. Luke then managed to make it safely back to Mount Olympus before anyone noticed his absence.

The Lightning Thief
Although Luke succeeded in his mission, his failure to defeat Ares cost him dearly. Kronos punished him with nightmares, and Luke swore never to fail the malevolent Titan again. This would also cause him to fear Kronos greatly for many of his later years.

When Luke was about nineteen, he was told in a dream from Kronos that another camper would be coming to Camp Half-Blood, one who would willingly (but not knowing) take the stolen weapons of the gods down to Tartarus, therefore ensuring that there would be a war. Luke remembers this and finds this camper in the form of a twelve-year old boy named Percy Jackson.

Knowing that Percy was the boy that Kronos was talking about, Luke befriends the boy and is successful in earning his trust and friendship. He welcomes him into the Hermes cabin (where children who haven't been claimed yet go), trains him in sword combat, and provides the moral support that Percy needed as a newcomer.

One night after a Capture the Flag game, he summons a hellhound to attack Percy in an attempt to make Chiron, the camp activities director, believe that the camp isn't safe for Percy. The centaur went for the bait. Unaware of Luke's treachery, Chiron sends Percy, along with Annabeth and Grover, to find the Master Bolt in order to prevent a war. Because monsters of Hades were unusually active and because it was as yet unknown that the Helm of Darkness was also stolen, it was believed that Hades was the Lightning thief and the group set out to go to the Underworld. Before Percy goes on his quest, Luke gives him a pair of winged shoes as a gift. These shoes were actually cursed to drag him, along with the Master Bolt, down into Tartarus when he neared it during his journey into the Underworld. However, this failed when Percy gave the shoes to Grover because Percy shouldn't fly as Zeus is the Lord of the Skies and does not like Percy. Grover managed to escape from the burden when the time came.

After Percy discovers that the Master Bolt was in a backpack that Ares had given him and he had won the Helm of Darkness in a duel with Ares (who was unknowingly being influenced by Kronos), Percy returns alive to Camp Half-Blood along with his two companions after returning the Bolt to Zeus, thwarting Kronos' plan.

In order to prevent Percy from interfering again, Luke takes Percy in the woods to 'look for something to fight.' While talking with Luke, Percy begins to slowly see Luke's dark side; Luke's words are bitter and he mentions his sword, Backbiter, which is able to kill both monsters and mortals. He says he will escape and then summons a pit scorpion to poison Percy. Luke tells Percy of his bitterness and desire for revenge, as well as his allegiance to Kronos, saying that there will be a new "Golden Age" that Percy won't be a part of before teleporting away. Though the assassination attempt on Percy fails, the scorpion does sting him and it leaves an asterisk shaped scar. Before losing consciousness, Percy kills the scorpion and the wood nymphs bring him back to camp for healing.

Luke's betrayal was a surprise to many campers and counselors, especially to Annabeth, who reacted with great sadness at the loss of another childhood friend. Annabeth, however, admitted that Luke had been acting oddly ever since his failed quest and eventually admitted to herself that her dear friend was indeed a traitor and said "May the gods curse him."

At some point before running away to join Kronos, Luke confronts Silena Beauregard, charms her, and persuades her to become his spy by telling her that she would be saving lives. Afterwards, she wanted to stop being a spy for the Titans, but Luke blackmailed her saying that he would reveal her secret if she ever stopped and would harm Charles Beckendorf, her crush.

The Sea of Monsters
A year after his defection, Luke took control of a monster cruise ship called the Princess Andromeda, which serves as his base of operations. In order to render Camp Half-Blood defenseless and eliminate a major ally of the Olympians, he poisons Thalia's tree with elder python venom from the depths of Tartarus, with the help of a spy in the camp's ranks. The plan was to later 'allow' Percy and Annabeth to take the Golden Fleece and heal Thalia's tree, so Thalia would be purged from it. He also frames Chiron for the poisoning, causing him to be fired from the camp and be replaced by Tantalus.

At first, Clarisse was sent to find the Golden Fleece and save Grover from the cyclops called Polyphemus but was interjected by Percy Jackson, along with a group of allies consisting of Annabeth Chase and Percy's half-brother Tyson, who is a cyclops.

Hermes, Luke's father, persuaded Percy to go on this quest, and told him to go onto the Princess Andromeda, hoping that he would meet up with Luke and convince him to stop his assault on the gods, and to tell him that his dad did love him. Hermes gave Percy some traveling provisions and sent Annabeth and Tyson to him. Together, they sped out to the Princess Andromeda to confront Luke. Percy and his allies landed aboard the Princess Andromeda, not knowing of its true nature (a ship with monsters serving Kronos), and were captured.

During this time, Luke told the two of his plans to use the Golden Fleece to complete Kronos' resurrection and attempts to recruit Percy and Annabeth to his cause (not willing to recruit Tyson as he reminds him of the cyclops that captured him and Thalia years ago). The two refuse, prompting Luke to order his bodyguards to feed the trio to a Drakon. Percy and the gang escape through a lifeboat propelled by the thermos containing the four winds given to him by Hermes.

Luke later intercepts Percy and his friends when they are looking for a boat that they can use to get back to camp. When he is interrogating Percy for the fleece in front of a pool (his army of monsters watching), Percy uses the pool to send an Iris message to Dionysus at Camp Half-Blood, tricking Luke into revealing the fact that Chiron was framed for the poisoning, resulting in Chiron being rehired (using the fact that he was in a panic due to Percy giving the Fleece to Clarisse). Enraged, he ordered Percy and his friends to be killed. Percy convinces Luke to duel him, a moment both had been waiting for a long time. Luke, normally would not do something so blunt, but he had no choice as his army would think he was weak if he didn't. Luke easily defeats Percy even when the latter's power is augmented by the water, but is prevented from killing him when he's knocked into the pool by a boxing glove glued to an arrow. The arrow was shot by Chiron and his family of centaurs (the Party Ponies) who had just arrived and proceeded to save them. When Percy escapes, Luke's spite and hatred for the son of Poseidon only increases.

Thalia is resurrected at last. It is possible and very likely that Luke's allegiance to Kronos was affected after this. He obviously wanted Thalia to be resurrected, shown when he says to Percy that he was going to give him the Fleece after he was done using it to resurrect Kronos. He believed, that Thalia would be on his side, after all the times they had spent cursing the gods, when they traveled together.

The Titan's Curse
After Thalia's resurrection, Kronos' second in command, Atlas, devises a plan to capture the Ophiotaurus, which would grant the power to destroy Olympus to whomever killed it and burned its entrails. He remembers the Prophecy and chooses Thalia to be its killer.

Luke is assigned to aid Atlas with this. However, Thalia and Luke were childhood friends, bringing Luke hesitation to carry out the mission. Knowing this, Kronos tells Luke that if he doesn't succeed in this mission, he would be chosen to be Kronos' host and therefore suffer a fate worse than death. This continues to become true in The Battle of the Labyrinth.

Luke carries the sky in a plan to trick Annabeth into holding it after she is captured, which succeeds. He and Atlas later use this to their advantage by forcing a captive Artemis to hold the sky in Annabeth's place, and Luke seems happy that Annabeth survives. Atlas orders the death of Annabeth, but Luke convinces Atlas to keep her alive until the Winter Solstice because he knows that Percy will come for her.

Luke is later seen with Atlas when he summons Skeleton Warriors to hunt down Percy Jackson. His final appearance is when Percy, Thalia and Zoë, arrive at the regrowing fortress of the Titans, where Artemis and Annabeth are being held captive. Refusing to have to kill Thalia, Luke attempts to sway her into joining their side. Thalia refuses and the two engage in a duel. The ferocity and power demonstrated is incredible, but Thalia ultimately wins the duel, disarming and injuring Luke, cornering him against the edge of a cliff (she claims that she was always able to beat Luke in a duel). Luke continues to goad Thalia ("Is that what you want? To go back to your dad in triumph?"), but Annabeth begs her to spare him. As Thalia and Annabeth argue over his fate, Luke attempts to use the opportunity to try and disarm Thalia of her spear, but she instinctively kicks him off the cliff, something that causes her both guilt and grief.

Although his body is seen by both an approaching army of monsters and Percy, it is later revealed that Luke survived the fall. It is unknown how he survived the fall, although it may have been due to Kronos' magic. A theory is that Kronos reversed time for Luke and turned him back from dying.

After her battle with Luke, Thalia pledges herself to Artemis in order to stop the prophecy from coming true through her, as she was only a few hours away from becoming sixteen. This means, that she is passing the prophecy onto Percy or Nico.

Poseidon later notes that the only way a non-Titan/god may take Atlas's burden is through their own free will and if they are a hero with great strength, a true heart, and great courage. Percy points out that Luke was able to take on the Titan's curse and then tricked Annabeth into taking the sky and then used Annabeth to lure Artemis into taking the sky from Annabeth and Poseidon says that Luke is an 'interesting case' and then is distracted.

The Battle of the Labyrinth
Not long after the battle atop Mount Tamalpais, Luke approaches Annabeth under a flag of truce. He begs her to run away with him, as the thought of becoming Kronos' vessel (host) apparently becomes too much for him. He says they could runaway, like the old times, fighting monsters and being a family. Annabeth is suspicious, however, and refuses, despite her determination to save Luke. Annabeth later regrets her decision, something that becomes very clear when Hermes confronts her and blames her for Luke's fate, in a fit of anger. Luke himself is also hurt by the experience, as implied by Kronos when he states that Luke learned not to trust his friends the hard way.

After the meeting with Annabeth, Luke continues to serve Kronos and prepare to become his vessel. His demeanor becomes marginally softer as he occasionally displays a moral compass that was previously unseen. This is most obvious when Luke becomes furious with Kelli for killing a boy in Seattle and when he indicates that he disapproves of Kampê's release, as she is too chaotic. He makes an attempt to talk with Annabeth again at Antaeus' arena, but this fails when she and her companions escape. He is also seen in many of Percy's dreams.

When Luke is last seen, he is possessed by Kronos and rises from his gold coffin. He tries to attack Percy Jackson, and is only stopped by the combined efforts of Rachel, throwing a blue hairbrush that hits him in the eye, and Nico, who calls a black rock that blocks Kronos' exit and stops him and the Telekhines from following them.

The Last Olympian
For the largest part of the war, Luke is almost completely controlled by Kronos, with a few moments of wavering in the Titan's control. In this time, Percy learns that when Kronos achieves full power inside of Luke's body, he will burn through Luke's body and attain his true immortal form, which would mean the end of all life near him (except for immortals).

Kronos made his way to the throne room of the gods with Ethan Nakamura, destroying the city of Mount Olympus as he did so. Meanwhile Percy, Annabeth, Grover, and Thalia follow closely after. A statue of Hera falls and would have killed Percy and Annabeth if Thalia had not pushed them out of the way. Thalia's legs are trapped under the statue and the others continue on. Kronos battles them in the throne room when they arrive, but Annabeth is able to catch Luke's attention, reawakening him, but only partially.

Ethan betrays Kronos after Percy persuades him, and attacks the Titan, unsuccessfully of course, as his sword shattered against Luke's invulnerable body. Several shards lashed, broke and bounced back at Ethan and impaled him, and he staggered to the ground. Kronos, now having another internal struggle with Luke, opens a fissure in the floor beneath Ethan, and he tumbled to his death. Kronos continued to battle the trio, getting closer to his ultimate transformation to his original self in which he would be unstoppable.

Annabeth managed to coax Luke back to his own mind as she lay, bloody, on the floor. Luke (still fighting against Kronos) lets Percy knock Backbiter into the hearth, leaving Luke defenseless. A beaten Annabeth gives Percy her knife, as they both realized that Luke was the true hero of the prophecy. Percy gave the knife to Luke who stabbed himself in his Achilles heel, which is located under his left arm, close to the underarm.

Percy, Annabeth, and Grover look away, hearing an explosion and Kronos' fading screams. Luke is left lying on the floor, dying. Annabeth says that he would go to Elysium and Luke replies "Think … rebirth. Try for three times. Isles of the Blest." Annabeth replies that he "always pushed himself too hard". Then, Luke asks Annabeth if she loved him. Annabeth replies that she loved him like a brother. Luke then pleads to Percy to not let this happen again. With that, Luke dies just before the gods arrived after defeating Typhon. In the end he is taken away by the Fates, blessed by Hermes, and remembered and honored as a hero by not only Percy, Annabeth and Grover, but by all. Percy realizes that the blue string he saw the Fates cut in The Lightning Thief, was not his, but Luke's.

The Lost Hero
Luke is seen in pictures belonging to Thalia in Cabin One. When Jason asks Annabeth, who looks pained, who he is, she says "That's Luke. He's dead now." signaling Annabeth has still not gotten over his death yet. Jason then wonders if Percy Jackson wasn't the only boy Annabeth had ever liked.

The Son of Neptune
Although there is no direct mention in the book, there is a hint of him. During Percy's first meeting with Octavian with Hazel, Percy tells Octavian that he reminds him of someone. Although Percy can't put his finger on it, Octavian shares resemblance to Luke.

The Mark of Athena
While fighting Chrysaor, Percy hears the voice of Luke (without meaning to), his old mentor, throwing out suggestions on how to fight the pirate. Later after watching Bacchus just sitting back as he and Jason fought for their lives, Percy realizes that he is about the same age Luke was when he turned against the gods. Percy also admits that he can understand how Luke became so spiteful, as Percy himself had also been used by the gods many times.

Personality
Luke showed his darker side as a villain for most of the series, so his character was mostly described as 'evil', however he was a hero in the end, so his character did malevolent things but was ultimately good at heart. In this way, he is more 'heroic' in the old sense of the terms, such as the stories of Theseus, Jason or Hercules. Apparently, Kronos chose Luke to host him because he had a strong spirit.

Appearance
Luke is described as a tall, handsome young man whom all the girls liked, with short-cropped sandy blonde hair, blue eyes, an athletic and muscular build, and a sneaky look like all Hermes demigod children. He is described through the series as being college-aged. Many girls are attracted to him, even an Empousa named Kelli. The only thing un- attractive on Luke is a thick, deep pale scar that runs from the bottom of his eye down to his chin. It is said that the scar was caused when Luke stole a golden apple and was then clawed by the guardian dragon (Ladon) of the tree.

Although he is generally very attractive, his appearance has varied over the books. In the first two books The Lightning Thief and The Sea of Monsters he looks as always did in Camp Half-Blood, but come The Titan's Curse, he begins to look sickly and aged. His usually tanned skin becomes ghostly pale, and his hair is also white (supposedly with gray streaks possibly from holding the sky), especially under the moonlight. He also begins to wear traditional Greek clothing, such as a white chiton and himation (used as an over-the-shoulder cape). However, in The Battle of the Labyrinth, Luke's healthy appearance returns as he gets closer to being taken over by Kronos. This is possibly because he bathed in the River Styx. He wore a white chiton and himation, which made him look timeless. Percy thought he looked too healthy, because his skin had an unnatural glow to it.

Abilities

 * ADHD: Like all demigods, Luke possesses inborn supernatural battle reflexes and senses that he uses to analyze the fighting style of his opponent.
 * Fighting Skills: Luke has been trained in hand-to-hand combat during his stay at Camp Half-Blood.
 * Swordsmanship: Luke is an expert swordsman, undoubtedly one of the best swordsman at Camp Half-Blood. In The Lightning Thief, a Hermes camper stated that Luke was "the best swordsman in the last three hundred years" In addition, near the end on the first book when Luke was revealed to be the traitor he claimed he could have beaten Ares if he, Luke was more cautious. In The Sea of Monsters, Luke easily defeated Percy, even when the latter's power was temporarily augmented by water. In The Titan's Curse, Luke was able to hold his own against Thalia before being ultimately defeated.
 * Dyslexia : His brain is hard-wired for reading Ancient Greek instead of modern languages.

Demigod Abilities

 * Can magically break locks.
 * Able to steal things without people noticing, even gods, such as the Master Bolt and Helm of Darkness.
 * Intuition: Luke can sense traps and demigods.
 * Teleportation
 * Alchemy: Luke can create and find the recipe for magic potions, e.g. Greek Fire.

Kronos Abilities
These are abilities given to Luke once he was under the service of Kronos:
 * Invincibility after bathing in the River Styx.
 * Chronokinesis: Once possessed by Kronos he could control time.
 * He has low levels of magical abilities, being able to move three chairs in The Sea of Monsters.

Weapons
Luke carries the half Celestial bronze and half tempered steel sword called Backbiter. Unlike Percy's sword Riptide which can't hurt mortals, (as they aren't "important enough to kill") Backbiter can hurt mortals. However, it is not believed that he ever did hurt any mortals with it. It's made from Celestial bronze and mortal steel. The two metals that the sword is made from are opposites, having magic fused with mortal metal. Percy could sense that the two metals were trying to escape each other during the forging, and that someone (most likely the forger) died in the creation of the sword. In The Battle of the Labyrinth, Backbiter is reforged into its original form - the Scythe of Kronos. Backbiter is named so as it will "bite back" at the gods who imprisoned Kronos in Tartarus. Kronos has the ability to turn his scythe back into Backbiter, as he does in the final battle at Mount Olympus. Backbiter, in The Ultimate Guide, is said to have been used to kill Ouranos. He also used to carry a bronze knife given to him by Halcyon Green, which he himself later gave to Annabeth when they met.

Annabeth Chase
Before Luke died, he asked Annabeth if she loved him, but Annabeth said that for her, he was like a brother. Though since The Lightning Thief, Annabeth showed great concern, loyalty, and admiration to Luke.

There were many hints throughout the series that Annabeth had a crush on Luke. When Luke hugged her, Percy said that she looked like she was going to pass out. Also, in The Battle of the Labyrinth, Luke was the "love" Annabeth had lost to a fate worse than death. Percy is shown to be extremely jealous of Annabeth's unrequited crush, though he tries to play this off as his own hatred for Luke. Percy stated that Luke was one of the reasons (along with Calypso and Rachel) that made his relationship with Annabeth complicated at the end of the fourth book. The most obvious clue was when Jason wondered if Annabeth had a crush on Luke from the way she talked about him and looked at his photo.

Annabeth's crush was most likely one-sided, as she is seven years younger than Luke. Luke, however, obviously cared a lot for her, and likely thought of her as a younger sibling.

Thalia Grace
It is hinted that Luke and Thalia may have been involved in a romantic relationship before Thalia had sacrificed herself at Half-Blood Hill (shown when Thalia kissed him on the cheek in The Demigod Diaries), but that dissolved when Luke poisoned Thalia's tree in The Sea of Monsters. Thalia seems to dislike Zoë Nightshade in The Titan's Curse because she had appeared to Thalia when she was with Luke and she told Thalia he would let her down (like all men). She is seen crying as she fights him in The Titan's Curse. After Thalia saw how far Luke had fallen and that Zoë was right, she turned her back on men and joined the Hunters.

Empousa
""I'd hate to see your handsome head on a spike.""

- Kelli to Luke, tracing his arm with her finger

Kelli, the cheerleader empousa, seems seductive towards Luke Castellan and seems to be trying to romance him. Luke however, is not swayed and ignores her hints, as he calls her a 'demon'. This may be, that the empousa feed on young men and male demigods, by seducing them with their pretty faces, before eating them. However, in The House of Hades, it was mentioned that Kelli was probably was attracted to Luke, as the son of Hermes had that effect on girls, according to Annabeth.

May Castellan
Soon after Luke's birth, May tried to take in the spirit of the Oracle, but failed as Hades had cursed the Oracle during WWII so that her spirit would never move on. May suffered several side effects for many years, such as seeing glimpses of the future. She even saw Luke's fate and would go into spats of screaming that scared Luke growing up until he ran away from home. He eventually went back with Thalia and Annabeth to get supplies, which was when he met his dad, Hermes. He ran away again and eventually made it to Camp Half-Blood. His mother still waited everyday for him to return and made him sandwiches and cookies.

Hermes
Luke felt that Hermes abandoned him and his mom and because of that, hates all the gods. He grows to dislike Hermes more when he gives him a quest that had already been completed by another hero, Hercules. However, he failed in his quest to steal a golden apple and was left with a scar to remind him of his failure.

Hermes, on the other hand, loved his son very much and sent Percy to try and bring him back in The Sea of Monsters, but was disappointed when he wasn't able to. He also becomes angry at Annabeth, because she chose not to join him in The Battle of the Labyrinth, before Luke became Kronos' vessel, though Hermes is shown telling Percy that it wasn't her fault in The Last Olympian.

The Lightning Thief
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As in the novel, Luke is the true antagonist of the film. He is portrayed by Jake Abel.

There have been some changes to his character, one of the most notable being that Luke claims he has never met his father, despite the fact that in the book series their only meeting has a profound effect on their relationship and the way Luke views the Olympians. The relationship between Annabeth and Luke, which plays a key role in The Titan's Curse and especially in The Last Olympian, is not as close as their book counterparts, seeming to be only acquaintances rather than lifelong friends; Luke's back-story is also cut. Luke's scar was inflicted by Percy rather than Ladon, the dragon in the Hesperides garden. Finally, there was no mention of Luke's association with Kronos, heavily implying that Luke acted alone. It remains unclear if there has been any contact between the two at all.

Luke's cabin was also filled with modern-world paraphernalia and he is seen playing Call of Duty: Modern Warfare 2, using a L86 LSW (with red dot) on the map Favela online. He apparently supplies his fellow campers with modern technology.

Luke's role remains mostly the same throughout the movie, however Luke and Percy's final confrontation has changed. Upon discovering that Luke is the Lightning Thief in the Underworld, they confront each other atop the Empire State Building. The two battle, with Luke gaining his scar and the Master Bolt changing hands several times until Luke seemingly has Percy defeated. When he questions whether or not Percy truly is the son of Poseidon, Percy uses the contents of several water towers and knocks Luke off the building and into the nearby ocean, leaving his fate unknown.

The Sea of Monsters
Luke returns as the primary antagonist of the film, with Jake Abel reprising his role. He also appears in the film's opening scene- Thalia's sacrifice and subsequent transformation into a tree- played by Samuel Braun.

As in the novel, he poisons Thalia's tree, but he also leads two Colchis bulls into Camp Half-Blood. Following the bulls' destruction, he encounters Percy near the Big House and informs the latter of his plan to revive Kronos.

Later, as Percy meets the Oracle, he learns that he (the son of the sea) will grapple with Luke (the Lightning Thief) for the Golden Fleece.

Luke later abducts Grover with Chris Rodriguez's help in Washington, DC. He also meets up with Percy, Annabeth, and Tyson on his yacht, the Andromeda, detailing his plan, and proceeds to imprison the three. The heroes escape the next day, despite Luke's efforts to stop them.

The heroes, now with Clarisse, obtain the Fleece and Grover, but Luke swipes the Fleece away (seemingly killing Tyson in the process) and proceeds to restrain them while reviving Kronos. When Kronos is revived, Luke greets his master, but is eaten by the massive Titan.

After Kronos is defeated, Luke is ejected into Polyphemus's lair and is cornered by the Cyclops, about to be eaten. It is unknown if Luke survived, but it is highly likely.

Video Game
In the video game, Luke is one of the main characters until the player has defeated Hades. His attacks are mostly poison-based, unlike the books where he fights more with his sword. The others being Isaac and Grover, he is one of the three characters that can grant Haste to a party member. He is resistant to Poison. He is also the final boss in the game where he is fought alone by Percy.

Trivia

 * In The Lightning Thief, Percy mentions that Luke's scar is under his right eye. However in Luke's official portrait, it is located under his left eye.
 * He is Hermes's favorite son, though this is only discovered in The Last Olympian.
 * According to May, his mother, Peanut Butter & Jelly sandwiches and Chocolate Chip cookies are Luke's favorite snacks.
 * Luke happened to be fond of "Kool Aid" (when he was younger).
 * His surname "Castellan" means a governor or warden of a castle, it also means 'someone who guards the castle'. Interestingly, he was the head councilor of the Hermes Cabin, which would also take in all new campers. He was also the one who saved Olympus from destruction.
 * The Diary of Luke Castellan is in his point of view.
 * In the The Diary of Luke Castellan, it is revealed that Halcyon Green had made a 14-year-old Luke promise that he would learn from his mistakes, something Luke misunderstood to mean not to be pushed around by the gods. Thus, Halcyon was the first one to inspire Luke to question the gods.
 * The main reasons why he sided with Kronos were that he couldn't get over the gods doing terrible things to their children; like Hermes's abandoning him, Apollo's cursing Halcyon Green, and Zeus's not saving Thalia.
 * Octavian bears a striking resemblance to Luke, causing Percy Jackson to think he knew him.
 * Luke was the last known person to die in the Second Olympian War.
 * Luke and Percy are alike in several ways:
 * They are both excellent sword fighters.
 * At some point they were both in the Hermes Cabin.
 * Both of their mothers can see through the Mist.
 * Both of them have bathed in the River Styx.
 * Both of them saw Annabeth while bathing in the River Styx (For Luke, he also saw Thalia).
 * Both of them are their father's favorite sons.
 * Both of them have met Ladon the guardian dragon.
 * Both of them are subjects of the First Great Prophecy.
 * Both of them held the weight of the sky, and escaped.
 * Annabeth Chase was interested romantically in both of them at one point in time, though Luke didn't return her affections.
 * They were both possessed by a figure from Greek mythology, turning their eyes yellow (Kronos, eidolon).
 * In the books, Luke's scar is caused by a dragon, while in the movie, it is caused during the fight against Percy at the end of the movie.
 * Luke's father, Hermes, is known as the god of thieves. Coincidentally, Luke was the one who stole Zeus' Master Bolt and Hades' Helm of Darkness in The Lightning Thief.
 * Luke is similar to Jason Grace in several ways:
 * They are both accomplished swordsmen.
 * They both have a scar on their face (Luke's diagonally across his face, Jason's on his lip)
 * They were both possessed by a figure from Greek mythology, turning their blue eyes yellow (Kronos, eidolon).
 * They are both considered physically attractive and charismatic.
 * They both hurt a girl who had feelings for them (Thalia Grace, Reyna Avila Ramírez-Arellano).
 * They both have blond hair and blue eyes, albeit with a slightly different build.
 * They both have a history with Thalia Grace—Luke was her oldest friend, and Jason is her long-lost brother.
 * They both are repeatedly compared to Percy Jackson.
 * They both wielded a blade given to them by a deity (Backbiter, Juno's gladius).
 * They both destroyed a Titan (Kronos, Krios).
 * Both of their mothers were unstable -- May Castellan was turned insane when she tried to become the Oracle of Delphi, and Ms. Grace was unable to hand her having summoned Jupiter/Zeus.
 * They both led an attack on a deity's throne room—Luke (while being controlled by Kronos) led an attack on Mount Olympus, and Jason led an attack on Mount Othrys simultaneously.
 * Luke's paternal grandmother, Maia, is thought to be the namesake for the month of May. Ironically, that is Luke's own mother's name.

Gallery
Luke Castellan

Luke Castellan