About Stiles Stilinski
Despite his very normal appearance, Stiles isn't your average teenage boy. His best friend is a True Alpha werewolf named Scott, and he is surrounded by other werewolves, hunters, a banshee, and a host of other supernaturally-inclined individuals. He's very protective of certain people in his life, and if you intentionally hurt one of them, he'll probably hold a grudge against you forever. He tends to jump headlong into dangerous situations without always thinking things through, and he has the general mindset that he's the expendable member of the pack due to his lack of abilities. Stiles himself may not be quite as average as he believes himself to be, either.
While he presents to most as being somewhat of a smart ass, ADD teen, Stiles is actually very smart and tends to be ahead of the game when it comes to figuring out the weirdness that happens in Beacon Hills. He's also a loyal friend and son, and fills the role of "sidekick" to his best friend Scott McCall, who is a werewolf. Stiles has a lot of gut feelings, and he tends to trust them because they're usually right. Whenever there is trouble, Stiles somehow finds himself in the middle of it with his friends, trying to figure things out and make them better.
While he does get angry sometimes, he also generally suppresses it and channels it into something more positive. He's not afraid to call someone out when they've done something wrong, even if it's someone he loves, like Scott. Once he's attached to someone, such as Lydia or even Derek, he's protective even when it puts his own life on the line. He tends to feel guilt when it comes to the death of his mother, though it's never been revealed why. He also feels guilty anytime something threatens his dad that stems from the weirdness that he's involved with. His love for his family and friends is both a strength and weakness. When things get to be overwhelming to Stiles, he has panic attacks.
Stiles' life changed when Scott was bitten and became a werewolf. He's a bit more intense and paranoid than he used to be.
Stiles is the only child of Beacon Hills' Sheriff Stilinski and the now deceased Claudia Stilinski. Stiles' mother died when Stiles was eight years old, from a long battle with frontotemporal dementia. He was with her when she died, while his father was out on the scene of a car crash. Sheriff Stilinski showed up at the hospital to find Stiles sitting in the waiting room with his head in his hands after his mom has passed away. He blames himself for her death (for unknown reasons at this point in canon), and he fears that one day his father will blame him for it, too. His greatest fear is that his father will not only blame Stiles for Claudia's death, but also that he will regret having Stiles at all.
His closest relationship aside from his dad, is with his best friend, Scott McCall. They grew up together and have been best friends for as long as they can remember. Stiles was the first to figure out that Scott was becoming a werewolf after he was bitten by a wolf in the woods. He stood by Scott's side and did everything he could to help him deal with all the challenges that come with being a werewolf. Ever since Scott was turned, Stiles' life has been pretty weird. It also brought new people into their circle of friends: Allison Argent, Derek Hale (though his relationship with Derek is complicated and he alternates between being afraid of the man and being annoyed with him, to actually feeling sympathy and protectiveness toward him), Isaac Lahey, Lydia Martin, Cora Hale, Jackson Whitmore, Boyd and Erica Reyes.
Whenever there is trouble, Stiles somehow finds himself in the middle of it with his friends, trying to figure things out and make them better. He frequently fears for his father's safety and finally tells him the truth about the supernatural goings on in Beacon Hills. Sheriff Stilinski gets angry with him, not believing him, and when Stiles asks Cora Hale (another werewolf) to show him proof, she faints to the ground unconscious.
He's been in love with Lydia Martin since the "third-frickin'grade" even though it's an unrequited love. The two share a kiss when Stiles begins having an uncontrollable panic attack after his dad is taken by Jennifer Blake (who turns out to be a being called a Darach, who feeds off the energy of human sacrifices in order to appear as a normal human).
He and Allison and Scott agree to be sacrifices of their own in order to save their respective parents. They are warned ahead of time by Deaton that they will return to life with a darkness around their hearts. The three carry through with the sacrifice and are brought back after seventeen hours, knowing where the Darach is holding their parents -- in an old root cellar. Scott goes to meet back up with Deucalion, and Allison and Stiles split up on separate tasks in order to save their families. Stiles is on his way to where they're being kept when the Darach causes a terrible storm. Stiles winds up crashing his jeep into a tree and gets knocked unconscious. He wakes up and makes it to where the parentals are being held captive in time to use his aluminum baseball bat to prop up the collapsing cellar.
Weeks later, after the Darach and the alpha pack have been defeated, Stiles and the others begin experiencing unsettling side effects from their sacrifices. Stiles is having nightmares that he has to scream himself awake from, as well as being unable to determine the difference between his dream life and reality.
When a killer named Barrow shows up looking for new student Kira Yukimura, Stiles puts the pieces together in time to stop him from harming her. Then he begins to realize he may have been the one to send Barrow after her. He tells Scott but Scott assures him that it couldn't have been Stiles, and tells Stiles to get some rest. He seeks out Melissa McCall's assistance and she sedates him so he can sleep for awhile. When he wakes up, he wanders down the hall only to be confronted by three demons called Oni. To his own surprise, he kills them with his bare hands.
Shortly after it's revealed that he is possessed, Stiles ends up sleepwalking to a cave in the woods and calling Scott for help. He hallucinates that he is in the basement of Eichlen House -- the local mental institution. Though his dad, Scott, Lydia and the others look for him, it is Scott's parents who find him. He's taken to the hospital for an exam to make sure he's there. Stiles ends up getting an MRI. He reveals to Scott that the doctor is checking for symptoms of frontotemporal dementia -- the same disease that killed his mother in 2004. The doctor gives the results to Stiles' dad and Scott's mom -- he indeed is ill.
During the MRI, Stiles is completely taken over by the nogitsune. He threatens Kira's mother, almost kills Isaac through an electric shock, and disappears from the hospital. During this time, he causes a great deal of off-screen chaos around time, before resurfacing in the basement of Beacon Hills High School. He's immediately attacked by Aidan and Ethan, but Scott stops them before they can hurt him. He tells them he's himself, that he knows that the nogitsune has been making plans, and after a series of terrible "accidents," it's revealed he's still under the influence of the nogitsune and hasn't been himself at all. He's been feeding on the chaos, strife and pain that he's caused, and he injures Scott. Before he can do any worse damage, Deaton drugs him with wolf-lichen, which essentially puts the nogitsune spirit to sleep temporarily.
Afraid of hurting Scott or anyone else again, Stiles has himself committed to Eichlen House, where he meets back up with former coyote Malia Tate, whom Scott helped return to being a human earlier in the season. As it turns out, Malia's not very happy about being human again and she wants to get back to being a coyote. She agrees to help Stiles get to the basement of the Eichlen House if he can help her return to her former state. While the two of them are in the basement going over old records, they share a moment of passion, though it's unclear as to whether they slept together or just made out.
Stiles is retaken over by the nogitsune and flees the Eichlen House, setting an elaborate plan into motion that brings nearly everyone on his chessboard together in a battle to either kill him or save him. The nogitsune cuts Stiles' stomach open, releasing flies that infect and possess Isaac, Aidan, Ethan, and Derek. Ethan and Aidan end up almost killing each other, and then Isaac almost ends up killing both of them, stopped in time by Allison and Kira, while Derek turns on Chris Argent, who ends up freeing himself. Meanwhile, Scott and Lydia go into Stiles' mind and manage to separate the nogitsune from Stiles.
However, Stiles is very weak, in a lot of pain, and freezing cold. Scott is able to tell this immediately upon a simple touch to Stiles' hand as he begins drawing pain away from his best friend without even trying -- the first time this has occurred on the show. As the nogitsune grows stronger, Stiles grows weaker. The nogitsune -- Stiles' now evil doppleganger -- kidnaps banshee Lydia Martin to predict when the Oni are coming to kill him, and at the last minute, he snaps the last kitsune tail and is able to control them himself. While Scott and Stiles go to find Lydia in the tunnels beneath Eichen House, Allison, Isaac and Kira fight the Oni. Allison is killed with a sword to the stomach and dies in Scott's arms moments later.
Stiles feels immense guilt over her death, commenting that the only good thing is "it looks like I'm dying, too." As the rest of the pack forms a plan to kill the nogitsune once and for all, Stiles repeatedly states that if whatever they have to do to kill the demonic fox wearing his face, do it, even if it kills Stiles. Scott tells him that the plan is to save Stiles and that is the plan he's going with.
The nogitsune sets up an elaborate trick for Scott, Stiles, Kira and Lydia at the high school. It summons the Oni and tells Stiles that it's going to force Scott to kill Stiles in order to save everyone else. He tells the group that he has sent Oni to every place where Stiles has someone he cares about -- the sheriff's station, the hospital where Scott's mom works, the vet clinic where Deaton works. The final battle begins and the Oni begin fighting Scott and Kira. Stiles picks up Kira's fallen katana off the ground and places the point at his stomach, ready to kill himself to save his friends and family even as Scott yells at him to stop.