|“||Feel that Theo? That's the secret to taking power. Pain. Take their pain, take their life, take their power. It's all or nothing. You take till there's nothing more to give.||”|
Upon learning that the Dread Doctors had finally created a perfect Chimera host for the spirit of the famous Werewolf The Beast of Gevaudan, Theo became hell-bent on stealing the Beast's powers to presumably develop into a true Werewolf like he always desired. To achieve this goal, Theo resurrected four of the previously-deceased Chimeras that were considered as "failures" by the Doctors and declared them his "pack". Around the same time, he heard the story that Deucalion once led a pack solely composed of Alpha Werewolves like himself, as well as that Deucalion and his fellow Alphas had stolen the powers of their own Betas to become the most powerful pack the world had ever seen. However, the Alpha Pack was disbanded with Deucalion and Ethan Steiner as the only survivors and former members of the pack. Theo sent his new pack of Chimeras to track down and capture Deucalion, a mission that was successfully accomplished. Deucalion seemed to have become blind once more after the magic of the Darach Jennifer Blake seemingly wore off and offered Theo to teach him how to steal the Beast's powers in exchange for Scott McCall's eyes, a deal Theo immediately accepted.
During his time as a prisoner in the operating theater, Deucalion used his manipulation skills to get Hayden Romero, Corey Bryant, Josh Diaz and Tracy Stewart to believe that Theo was not who he said to be and only valued his "Betas" as pawns in his pursuit for more power, a tactic that drove all of them except Tracy to leave the Chimera Pack, all while he gave Theo information about the talons of the deceased Werewolf-Garuda Chimera Belasko, which he got from the Desert Wolf, killing him if he used them and tricked him into killing Josh and Tracy to steal their respective powers as practice to steal the Beast's powers.
Once Theo's attempts to confront the true Beast Sebastien Valet and steal his powers proved to be fruitless, he was confronted by Deucalion, Scott and Liam Dunbar, leading him realize that Deucalion and Scott were aware of his plans for the Beast and were working together to weaken him and break his pack in the same manner Theo turned the McCall Pack members against Scott in the first half of Season 5. Theo attempted to kill them all with the powers he stole from Josh but Kira Yukimura and the Shiprock Skinwalkers opened up a gate to another dimension and allowed the spirit of Theo's deceased sister Tara Raeken to banish him to Hell as punishment for his crimes.
His imprisonment in Hell certainly contributed to Theo's change and redemption in Season 6 and he proved this by helping the McCall Pack stand against the Ghost Riders and the Alpha Löwenmensch Garrett Douglas, as well as helping them face the ancient shapeshifter Anuk-ite and Tamora Monroe and Gerard Argent's Hunter Army while Deucalion kept himself out of the recent supernatural events in Beacon Hills. Theo and Deucalion never got the chance to reconcile before Deucalion, who was teaching Scott and Malia how to battle the Anuk-ite without their eyes, met his end when shot by Monroe's fellow Hunters with Wolfsbane-laced bullets.
Theo and Deucalion are often known as Theucalion by fans.
Throughout Teen Wolf Edit
In The Sword and the Spirit, Theo returned to the Dread Doctors Operating Theater with Belasko's Garuda Talons following a deal he made with the Werecoyote Desert Wolf. He noticed the members of his Chimera Pack Tracy Stewart, Josh Diaz and Corey Bryant sporting wounds from their efforts in capturing Deucalion, who was seen hooked up to the Dread Doctors's special Wolfsbane formula drip. Theo seemed disappointed in his packmates' prowess in taking down a blind Werewolf. This comment made Deucalion reveal that his blindness returned a while ago as Jennifer Blake's healing magic only proved to be temporary. They changed the subject to the newly-resurrected Beast of Gevaudan, who Deucalion described as the most famous and most vicious Werewolf in history and asked Theo if he thought he was going to show him how to steal its powers. Theo asked him what he wanted in return and the self-proclaimed Demon-Wolf stated dramatically that he wanted the eyes of Scott McCall on "the tips of his claws".
In Lie Ability, Hayden Romero was still "babysitting" Deucalion while Theo, Tracy, Corey and Josh were invading Eichen House to retrieve the Banshee Lydia Martin, knowing that she was connected to the Hellhound Jordan Parrish, who was prophetized to battle the Beast, and use her to draw both Parrish and the Beast to them. In the operating theater, Deucalion admitted to Hayden that he seemed to think that Theo was doubting of Hayden's loyalties and certainly left her to supervise Deucalion because she was the strongest and fastest after him in the pack. However, Hayden replied that she knew exactly that the reason she was left in the theater with Deucalion was because her romantic relationship with Liam Dunbar made her a liability in Theo's plans. Deucalion advised her that if she wanted to help her boyfriend and the other members of his pack, she should less worry about being a liability and trust in her "ability to lie".
Hayden received numerous messages from her friend Mason Hewitt, asking her for her help in disabling Eichen House's lockdown and rescue their friends trapped inside the mental institution. Deucalion encouraged Hayden to leave and help her friends, swearing that he would not be going anywhere when she returned. Not trusting in the Demon-Wolf's word, Hayden picked up a syringe full of Tracy's Kanima Venom and injected Deucalion with it to ensure in her own terms that he would stay in the lair for the time she would be gone.
After failing in getting Lydia, Theo chastised Hayden for using the syringe of Kanima Venom when it was meant for emergencies only. Deucalion guaranteed Theo that "a little dissension in the ranks" was perfectly healthy and asked him if he returned empty-handed. Theo admitted that while he did not succeed in capturing Lydia, he managed to get a Dread Doctor Mask that was in the possession of Dr. Gabriel Valack which could help him achieve the same ends by an alternative means. He would finally have the answer for his question: "Who is the Beast?".
In The Beast of Beacon Hills, Deucalion watched curiously as Theo and Tracy attempted to get Josh to wear the mask they stole from Valack. They insisted that the mask would kill them but Josh had similar electromagnetokinetic powers to those possessed by the Dread Doctors and those powers would allow him to safely see through the mask the information they were missing. Deucalion joined them, recounting the story of the Surgeon and how he built the first mask, infusing it with the deadly power of electromagnetic fields. Josh stubbornly refused to do it and ordered Theo to use it himself since he was the one wanting to know the identity of the Beast.
Tracy asked Theo about Belasko's Talons but Theo considered them "useless" given the fact that they did not yet figure out who was the vessel for the Beast. Deucalion was surprised to hear that Hayden did not tell Theo that the talons would kill him once he put them on before insinuating that both Hayden and Corey seemed to have deserted Theo. Finally realizing that Theo cared about no one but himself, Josh declared to be leaving, which only made Deucalion mock Theo even further about "his circle of trust narrowing". Visibly hurt by the truth of Deucalion's words but refusing to show it, Theo ordered Tracy to paralyze his tongue, an order which she gleefully complied, until she was asked by the blind Alpha how powerless she felt her entire life untiil her transformation into a Werewolf-Kanima hybrid as those who were powerless were always the ones who desired to show their newly-gained strength, comments that made Tracy think to herself.
Deucalion decided to finally reveal that he allowed himself to be captured and had been their prisoner in his own free will the entire time. He removed the wolfsbane drip from his arm and let it fall to the ground, scaring Theo, Tracy and Josh. Deucalion replied that he would teach Theo what he was waiting for so long and shoved him against a wall, breaking his arm and taking his pain right after. Deucalion told Theo that he had to take someone's pain, then that person's life and, finally, that person's power until there was nothing else remaining. Initially, it looked like Theo was about to engage in a fight with Deucalion but he decided to turn his attention to Josh instead, impaling him with his claws and absorbing his powers, which made his golden Chimera eyes glow brighter, until he died. Deucalion reprimanded Theo for eliminating a member of his "small and inexperienced pack", but Tracy agreed with Theo that Josh was the one small and inexperienced and she and Deucalion convinced him to put on the mask to prove his position as a real Alpha Werewolf.
The next day, Deucalion listened to Theo and Tracy's convesation with Scott and Liam about Mason being the vessel used by the Dread Doctors for the Beast's spirit. Once Scott and Liam left the locker room, Deucalion stepped out of his hiding spot and advised Theo to think very well on his strategy to incapacitate the Beast long enough to steal its powers. Theo explained that they wouldn't stop the Beast and tasked Tracy with paralyzing the Beast, but she became incredulous about this plan, especially when Parrish proved to be immune to her venom during their last battle against him. Deucalion pointed out that the venom did not work on a Hellhound but the Beast was still a Werewolf and urged Tracy to always keep her tanks full as they would need all she had.
While searching for Mason in the woods with Theo and Liam, Scott told his former classmate that he shouldn't have trusted Deucalion and listened to him, only for Theo to remind Scott that he was the one who let Deucalion go back in Season 3's Lunar Ellipse. Scott simply retorted that he wasn't a murderer, which made Theo question him if he thought he was going to get through all of these events without killing anyone, a question that Scott had difficulty to answer.
In Apotheosis, Deucalion came into the operating theater, just in time to witness Theo murder Tracy for her powers, just like he did to Josh the previous evening. Tracy attempted to fight back but her efforts were in vain and she died. Deucalion exasperatedly and dramatically announced "And then there were none."
Theo and Deucalion descended to the Underground Tunnels and heard one of the Argents' ultrasonic emitters. Deucalion advised Theo to be cautious and prepared for anything they could face, but Theo had plans of his own. He opened a circuit box and used its electricity to shoot a lightning bolt at Deucalion, shocking him and making him collapse on the ground, much to Theo's pleasure. Deucalion angrily warned Theo that sooner or later, his willingness to stab his allies and enemies in the back would eventually lead to his own downfall. Theo ignored this warning and left Deucalion on the ground, promising to bring Scott's eyes to him.
Deucalion recovered from the shock and joined Scott and Liam in confronting Theo after the latter failed miserably to steal Sebastien Valet's powers. Theo realized that Deucalion had been lying to him this whole time and was working with Scott to prevent him from killing the Beast; Deucalion smugly confirmed this. He removed his sunglasses and when he opened his eyes again, they were back to their healthy state and confirmed that he had also lied about Belasko's Talons not helping Theo steal the Beast's powers but they could have actually helped Theo if he did not believe in Deucalion's claims. Deuc wasted no time in incapacitating Theo further by breaking his neck to keep him from causing more problems for their side.
He wished the Chimera good luck with healing from his broken neck before he attempted to leave with Scott and Liam so they could save Mason together but Deucalion was shot in the stomach by Gerard Argent, furious with Scott and Deucalion's surprising alliance. Chris Argent tossed to Scott and Liam Marie-Jeanne's Pike so they could complete their mission while he dealt with his father.
While Deucalion recovered from his wound, Theo attempted to kill his enemies for killing the Beast but he was imprisoned underground by Kira Yukimura and the Skinwalkers, who summoned the spirit of Tara Raeken to drag Theo down to Hell. He spent the next three months trapped underground until freed by Liam and Hayden in Ghosted.