In Season 3, the Nogitsune is a 1000-year-old Void kitsune spirit who takes possession of Stiles Stilinski as 'Void Stiles' to cause chaos and strife throughout Beacon Hills, California. This malevolent Nogitsune was summoned from beyond by kitsune Noshiko Yukimura in 1943. Defying Noshiko's desire for revenge, he brough chaotic terror and carnage to Oak Creek. Noshiko took him down and imprisoned him using the Nemeton's power. Seventy years later, the druidic sacrifice undertaken by Scott McCall's Pack unleashed him from his dormant prison. Scott and his Pack combat the Nogitsune as they fight to save Stiles. Scott succeeds in splitting the Dark kitsune from Stiles, but the kitsune instead takes on Stiles' shape. Void Stiles then takes control of the Oni that were tasked with killing him. With his new servants, the Nogitsune kills Allison Argent and launches an assault on the entire town. Scott's Pack challenges the Kitsune in a game of Go. Stiles overturns the game with a divine move, breaking the Pack free of an illusion, Scott McCall and Kira Yukimura defeat him with an bite and a Kitsune's handheld weapon respectively and Isaac lahey imprisons him in a special urn crafted out of the Nemeton's wood.
The Nogitsune is a being of pure evil, having rescinded his humanity and sees everything as a game. Apathetic, self-absorbed, sadistic, malevolent, completely void of empathy, morals or values, the Nogitsune will seek to cause chaos and pain whenever he wants and wherever he pleases. His only purpose is to feed on the strife and chaos. He takes joy and pride in playing games with his victims before he puts them down. As with all Nogitsune he is very proud and can be blind when it comes to his weaknesses.
The Nogitsune is nigh immortal. Rendered to being just a spirit and over a thousand years old, the Dark spirit is no longer human, he is incapable of being permanently killed. He wields the very pinnacle of a kitsune's full power. His FoxFire manifests as his animal totem, houseflies.
He was summoned by the kitsune Noshiko Yukimura in 1943. Noshiko had prayed to her ancestors to send a Nogitsune to attach itself to her. Her intentions were so she could deliver justice upon the army soldiers at Camp Oak Creek for the manslaughter and the death of her great love Corporal Rhys. But because a Kitsune cannot and is not meant to be controlled, the Nogitsune tricked Noshiko and instead possessed Rhys' corpse, reanimating the clinically deceased corporal.
Angered that he'd been attemptedly controlled, to spite Noshiko, the Dark Kitsune unleashed his vengeance and chaos.
He came to Eichen House where Noshiko's fellow refugees allocated to after the massacre. He caused a bloodbath, he brought chaos, strife wherever he went. Soon enough, he was confronted by Noshiko, his former avatar. Noshiko wished to take responsibility for her mistake, and rectify the situation and she fought him. The Nogitsune was distracted by a werewolf, Satomi Ito and so Noshiko slew the Void Kitsune with her katana.
The sacrificial Druid ritual undertaken by Scott McCall, Allison Argent and Stiles Stilinski gave the Nemeton enough power which released the Kitsune from its prison. Eventually, the Nogitsune possessed Stiles at some point. Stiles was vulnerable to his control because the Druid sacrifice had left a door to Stiles' mind open.
The Nogitsune makes his first appearance possessing Stiles at Beacon Hills Hospital. Initially, his possession of Stiles was weak and sporadic.
During the skirmish at the power plant, the Void Kitsune had taken control of convicted serial killer William Barrow. Barrow was to kidnap and electrocute Kira Yukimura. However, unknown to Barrow the Dark Kitsune actually intended to fully awaken Kira's Thunder Kitsune trait. The Nogitsune had orchestrated the entire skirmish to use Kira's FoxFire to jumpstart his power, his possession of Stiles.
The Void Kitsune first appears when it is confronted by the Oni. One attempts to scan Stiles' spirit. He easily destroys three of the demons. Scott meets with "Stiles" afterward and the Kitsune follows his host's best friend with Scott none the wiser.
The Nogitsune appears in person to Stiles. Stiles is walking and talking in his sleep, while the Nogitsune is stalking the teenager within his subconscious, trapping him in an illusion. In the vision, Stiles is in pain, his leg is caught in a steel jaw trap. The Kitsune taunts Stiles refering to himself and Stiles as "we", saying it's a riddle. He riddles Stiles and the boy is able to answer some. Stiles is unable to solve the last; "Everyone has it, but no one can lose it. What is it?" The Nogitsune tortures him by pulling him along by the trap, but he vanishes when Stiles wakes up.
He appears to his host again during Stiles' MRI test. The Nogitsune threatens Stiles' friends and family saying unless Stiles has solved his riddle "we're'' going to destroy all of them. Stiles whimpers why. The Dark Trickster again riddles him. Stiles yells he doesn't know, but when he does he says "a shadow". The Nogitsune has taken off his bandages and reveals Stiles' own face taking possession of his body.
On the physical plane, Scott and Derek had discovered Stiles had tried to prevent the Dark Kitsune - himself - from cutting an electric cable on the hospital roof. Meanwhile, the Nogitsune wakes up in Stiles' body with the latter's personality rendered dormant. He translocates out of the MRI chamber. During the power surge, amongst the chaos, he faces off against Noshiko Yukimura, recognizing her. With the Oni by her side, Noshiko makes it clear to him she will have him killed even if his chosen host is an innocent. The Kitsune calmly walks off as the hospital's electric supply cable splits injuring and killing dozens.
When Stiles finally appears, Scott and his Pack believe he's himself again - only it's the Void Kitsune pretending to be him as "Void Stiles". He manuevers Scott into siphoning pain from various people so he can draw all the collected pain from him later and also to have the werewolf protect him from the Oni. He reveals his true identity to Scott when he's impaled with an Oni's sword. He sadistically twists the blade in Scott's gut, mocking Scott that he should have done his reading, that he shouldn't trust a Fox, that they'll fool everyone. Deaton appears at that moment and poisons Void Stiles with a shot of letharia vulpina temporarily breaking the Nogitsune's possession of Stiles. However Deaton says the Dark spirit is only poisoned, not dead.
Stiles has himself institutionalized in Eichen House, to prevent the Nogitsune from harming anyone again. The Dark Kitsune stalks him, appearing in his hallucinations, appearing as patients and doctors in his host's point of view. When Stiles is forcibly sedated, in a dreamscape, he is trapped inside a school locker. The Nogitsune appears. Stiles stands up to the Kitsune, telling him "Screw you and your riddles", but the Trickster answers "No riddles this time, Stiles." He demands to be "let in" - let inside Stiles' head and he'll let Stiles out of the locker. Malia Tate saves Stiles by waking him up.
The Void Kitsune continues his game with the protagonists. In Ken Yukimura's history classroom, he comes in, asking for Noshiko's final Tail. When Ken feigns ignorance, the kitsune has one of his flies scour down Ken's throat saying they always talk eventually. He leaves after it's clear the Tail isn't there. He allows himself to be caught on one of the Sheriff's home security cameras in Stiles' room. He ominously waves at the camera. He leaves clues to Allison Argent, Derek Hale, Sheriff Stilinski and Chris Argent that he's in Derek's loft.
The Nogitsune gathers the foursome at the loft. He pretends to be Stiles, with the Sheriff saying if he's his son, he'll allow his father to cuff himself because it's to keep him safe. He allows himself to be cuffed, but then later grins. Stilinski replies "You're not my son." The Nogitsune breaks the handcuffs with super-strength. He overcomes Allison's tazer, ripping the wires from the gun; Derek attempts to take him down, but he easily throws the werewolf aside. Chris pulls a gun on him, intending to put him down. The Trickster changes tactics, acting scared, pleading to Stilinski that Chris is gong to shoot him. The Sheriff takes the bait, demanding Chris he put his gun down, eventually pulling his own gun on the former hunter and yelling at him. Allison realises it's all part of the Kitsune's goal - strife. When the Oni appear he uses the foursome as bodyguards against the Oni. While they act as a distraction, the Nogitsune translocates out of the loft.
He corners Noshiko back in Eichen House's basement knowing she called off the Oni as a ceasefire. He grabs her last kaiken from her. He uses it to slice open Stiles' own stomach. The Void Kitsune declares "Chaos has come again," multiple flies emerge fromthe wound and he translocates out of the basement. The Nogitsune's flies enter the various werewolves around town Derek, Isaac Lahey, the twins and possess all four of them, having them to go on rage fests, becoming feral and going after old scores. They also attempt to possess Scott, but the Alpha is saved by a closed window. Stiles' body is found unconscious in the streets, with the wound healing and is brought to Scott's house, but Void Stiles is paralyzed by Deaton with kanima venom.
The Nogitsune holds Lydia at Camp Oak Creek. He taunts and stalks her, asking if the voices are louder than usual. He says the reason why is "a lot of bad things happened down here", references his mass murder back in 1943. The Trickster asks if the voices are saying that Stiles is dying. He affirms this as though Stiles is exorcised, he's still linked to the Nogitsune, in internal pain and freezing.
As night arrives, Lydia says she doesn't need to Scream to know he's going to die. The Dark Kitsune talks back that it's all part of his plan, this is why he's kept her, her power so close, so to know when the Oni would appear, when his own death would be upon him. When the Oni appear and surround him, he breaks Noshiko's last Kaiken with the Oni so close to him. The Oni are now under his control.
He and the Oni translocate to the opening yard, he unleashes the demons upon Isaac, Allison and Kira. The Nogitsune smirks and lazily watches as the Pack attempts to hold off the demons. He is not pleased when Allison succeeds in destroying one Oni. When Allison is killed, the Dark kitsune smirks then leaves with the his new servants.
Scott and his Pack, following the rules of the game of Go, arrive at the high school (a territory) for a final stand against the Dark kitsune. He traps Scott, Stiles, Lydia and Kira in a massive illusion featuring a Japanese garden in the wintertime. The Nogitsune appears in his corporeal incarnation, Rhys' corpse along with the Oni. He calls their location the place between life and death. Lydia identifies it as Bardo. Meanwhile at the school yard, on the physical plane, Derek and the twins face off against Void Stiles and two Oni. He taunts them calling them a "Pack of former Alphas".
Within "Bardo", the Nogitsune (his mental apparition) calls Stiles that everyone he cares about will die, just as the Trickster promised. He relays he's almost captured all the territories on the board, the hospital and the Sheriff's station. He makes a powerful gesture, and just then, says the animal clinic (two Oni simultaneously attack and wound Deaton). The Kitsune asks his host if he know the ritual of Seppuku. Stiles replies he doesn't want to know. The Nogitsune compares Stiles and his best friend Scott as a samurai, and his kaishakkunin respectively. If Stiles wants to save everyone touched by an Oni's blade (including Melissa, his dad, Deaton), then Stiles will disembowel himself, and then Scott is to kill Stiles first. The Nogitsune states and justifies his rules as "To win the Game".
Scott and Kira fight the Oni with all their might to no use. Derek and the twins have no such luck either in the physical plane. When Stiles decides to surrender, he picks up Kira's katana and places it at his abdomen. The Nogitsune eggs Scott on to kill Stiles, to give up the game. Stiles stops suddenly seeing reflections of books and school tables. The Nogitsune presses him, saying "(he) has no moves left". Stiles counters he has a divine move.
On the physical plane, Derek and the twins are losing. Chris Argent and Isaac arrive, and they begin killing the Oni with silver arrowheads. Void Stiles, upon seeing this, retreats back within the high school.
The Void Stiles shape cracks, collapses and disintegrates into dust, then air. With the Nogitsune's demise, all the people struck by an Oni's blade are healed due to the defeat of their master, putting an end to his threat.
House flies are the Nogitsune's animal represenation. They manfested as his form of FoxFire.
The Dark kitsune could use flies as messengers, if not embodiments of itself. The flies he could summon gave him mind control. Victims just had to have his fly present in their system, then the nogitsune could influence, direct their actions gradually to his will.
Victims of this process include: William Barrow, who had a tumor full of flies within his body, Oliver, Derek Hale, Ethan, Aiden, and Isaac Lahey. The nogitsune attempted to get information out of Ken Yukimura by making him swallow a fly.