Before Lightning Thief
Luke is son of Hermes and Mary Castellan. He left home at 9 yrs of age after his mom went insane. At age 14 he met Thalia and Annabeth and together they fought many monsters together.
While at his house healing his friends' wounds he is told by hid Dad that he knows his fate and when not told storms off all angry. After that he grew reckless, got into battles they didn't need to fight. Eventually they met Grover and the 4 try to make it to Camp Halfblood. In order for the others to make it, Thalia sacrifices herself and Zeus transforms her into a tree to save her. After that Luke kept on going down a dark path.
At the age of 17, Luke is sent on a quest to retrieve a Golden apple from the Garden of Hesperides. After his failure to complete the quest he is met with pity by the other campers and this made him hate Hermes and the gods of Olympus, soon being approached by Kronos to join him, which he gladly accepts.
He stole the Master Bolt and Helm of Darkness for Kronos and is caught by Ares and is only saved by Kronos' telling him what to say.
Luke was cursed by Kronos with horrible nightmares for his failure and he vowed never to fail the titan again. Luke is told that a camper will be coming to carry the bolt to the Underworld, and knowing that this person is Pecy is said person he befriends him, gives him moral support, and gives him sword training.
At the game of Capture the Flag he summons a hell hound to attack Percy. Percy is then sent on a quest to Hades' realm with Annabeth and Grover and is given by Luke a pair of winged shoes.
Percy gives the shoes to Grover and doesn't tell Luke which unknowingly saves his life from Tartarus.
When Percy returns to camp after sucessfully thwarting Kronos' plan, Luke must eliminate the problem any way necessary. Percy soon realizes he was behind everything and after refusing to join is poisoned by a pit scorpion who Percy kills and is dragged to camp to be healed.
Luke's betrayal was a shock to everyone especially to Annabeth.
The Sea of Monsters
A yr later, Luke poisons Thalia's tree and takes command of the ship Princess Andremeda. After capturing Percy, Annabeth, and Tyson he then lets them escape and lets them get the fleece for him. He soon reveals that he planned to let them use the fleece after he was done with it.
In order to keep Luke busy and keep the fleece safe, Percy gets Luke to duel him and Percy is easily defeated and is only saved when Chiron arrives with his "Party Pony" relatives
Thalia is resurrected thus revealing Kronos' big plan.
The Titan's Curse
Luke is seen serving the titan Atlas "The General". Luke held the sky until Annabeth came and saved him from the horrible burden. Luke and Atlas then use Artemis to take the burden from the weakened Annabeth.
Luke's final appearance is when Thalia kills Luke by kicking him off the edge. This however did not kill him and all the people are left wondering how he managed to survive.
The Battle of the Labyrinth
Luke serves Kronos throughout and continues to prepare to be his host. In one of Percy's dreams he sees Luke in a state of anger and disgust when seeing Kelli who killed a half blood. He is also seen as not liking Kampe.
Luke is last seen in the book as the vessel for Kronos.
The Last Olympian
He is under the control of the titan lord Kronos and is only seen in a few sections.
During the battle of Mt. Olympus Annabeth manages to get Luke partial control of his body and Luke ends up in the end proving himself a hero killing himself and the titan lord by stabbing himself in his Achille's heel(which was under his left armpit). Luke then asks Percy with his dying breathe that the minor gods' have their demigod children not be forgotten nor any demigods be unclaimed, and Percy promises.
He died a hero, a hero not just to Percy, Annabeth, Grover, and Thalia but all who knew of him.
Powers, abilities, and items
ADHD: This is a product of his battle reflexes
Dyslexia: It is highly probable he has Dyslexia and this would be a product of his mind's being hardwired for ancient greek
Swordsman: It is said that Luke was the best swordsman seen at camp in 300 yrs. And the only true challenge he ever faced was Percy who when they last thought dueled with neither gaining any significant advantage.
Teleportation: It is unknown if Luke's teleporting was a inherent power for children of Hermes or if it was given by Kronos or the sword Backbiter
Master Thief: As a child of Hermes he has great thieving skills
Summoning Pools of fire and Water: In Titan's Curse, Luke summons pools of fire and water. this is most likely one of the powers given by Kronos
Kronoskinesis(a.k.a. Time Manipulation): Once possessed by Kronos he could control time and manipulate however he wished.
Curse of Achilles: Luke took on the Curse of Achilles and was invulnerable everywhere except under his left arm
Control of Items of Luxury: It is possible he has minor control of items of luxury such as chairs which he moved with a flick of his hands.
Backbiter: Backbiter is a powerful weapon being made of both celestial bronze and metal thus being able to wound any creature known. Backbiter is later revealed to be Kronos' scythe. The maker of this metal forced the 2 metals together(the metals being angry to be together and fought to escape) and died making it.