The mythological creature known as the chimera is described as a lion with the second head of a goat's and a tail that ends as a snake.
Throughout Season 5, the Dread Doctors perform human experimentation on several innocents, recreating them into creatures of the supernatural, through science rather than mysticism. All of the recipients display traits from more than one supernatural creature as a result. These test subjects were dubbed Chimeras by Scott McCall due to them being hybrid creatures.
The Dread Doctors' aim was to discover, then gradually perfect the process to revive the perfect killer, the most notorious, most aggressive werewolf that ever lived: Sebastien Valet, the Beast of Gévaudan.
In the duration of the experimentation committed by the Doctors, through their breaking the laws of the supernatural, to revive the ancient werewolf, the paranormal conditions fell through for the Chimeras:
- The test subjects would have to have genetic chimerism
- the latest chimera test subject, if successful, would become the vessel for the Beast's spirit
- if the test subject were to bleed mercury-colored blood, they would be declared a failure for being the vessel
- to revive the Beast, the world's most perfect killer, the Doctors first needed a perfect 'true evil'
- the successful chimera would be the result of someone truly good being corrupted becoming a true evil
The Chimeras possess the traits of a particular supernatural creature they are remade into, but they are not supernatural, and so they are not affected by the every day arcane rules:
- they are able to handle mountain ash, as well as cast or cross barriers made out of said substance
- those who are converted into werecreatures are not beholden to the full moon
- those who are converted into canine werecreatures do follow the eye color rule (Theo Raeken)
- they are not drawn to a beacon of power and cannot find e.g. a Nemeton
The Dread Doctors chose particular young people for their experiment to create a potential Chimera. Each victim had a medical procedure prior to being altered by the Doctors. They'd received allogeniac tissue transplants, from an outside donor of the same species, i.e. skin grafts or organ and tissue transplants. Every one of the Chimeras were all genetically a chimera to begin with.
In 5x10 - Status Asthmaticus, the Dread Doctors' latest test subject Mason Hewitt is declared a success, and the spirit of the Beast is placed into Mason's body. The successful Chimera, Mason, becomes capable of sporadically transforming into an engineered version of the Beast of Gévaudan.
The Beast now lives again, killing it's way throughout Beacon County. However, Sebastian Valet is not yet resurrected, because of his name being forgotten due to 'damnatio memoriae'. When the werewolf shape of the beast, transforms back, Mason is left standing instead. The Dread Doctors, having completed their experiment, now seek to have Sebastian remember his name, by nurturing the Beast's transformations and murderous tendencies. The Doctors finally bring Sebastian back from the dead, effectively erasing Mason Hewitt from existence.
The Dread Doctors, having perfected the Chimera process, now want the Beast to remember itself as its original deceased human incarnation and identity, Sebasten Valet. The Dread Doctors use powerful sonic frequencies to trigger Mason's transformation into the Beast and arrange for the beastly werewolf to gradually remember more of its former life to also gradually bring back Sebastien from the dead. The Doctors succeed in their actions, the Beast remembering its real name and Sebastien is revived, leaving Mason Hewitt erased from existence, but lives on as memories. Mason is saved by Scott's Pack who have the Beast remember itself as Mason Hewitt and Mason is freed, separated from the Beast's spirit.
Theodore "Theo" Raeken is the very first Chimera produced from the Dread Doctors' experiments. Nine years prior to the series, Theo was chosen to be a Chimera by the Doctors. They saw him as a perfect candidate for being the 'perfect evil' as Theo was a sociopath: he would willingly murder his responsibly caring sister as a child. After Theo killed his sister, he sister, he became a genetic chimera after the Dread Doctors harvested his sister's heart and transplanted the organ into him. The para-scientists eventually failed with Theo, but his failure was a turning point in their research, so they allowed him to survive. Afterwards, Theo became partners with the Doctors. He served the Dread Doctors during Season 5 by being their spy amongst Scott's Pack as they conducted their most recent line of experimentation, to find then experiment with truly good test subjects being corrupted. After the Doctors killed off the failures, Theo forms a pack with four of the failures, bringing them back to life, Hayden Romero, Corey Bryant, Tracy Stewart and Josh Diaz.
Theo is a Chimera hybrid of both a werewolf and a werecoyote. He shows the physiological traits and powers of both shapeshifters, including pack symbiosis, a 'Beta' werewolf transformation, strength, reflexes, endurance speed and senses. His werecoyote part allows him to shapeshift into both a full wolf and a full coyote form. Though Theo is a killer, he permanently displays the gold eyes of an innocent and cannot rise to alpha rank in the supernatural sense. Theo then kills Josh and Tracy, to the steal their sparks of power, gaining the capabilities of a kanima and electrokinesis, producing kanima venom and his abilities and healing factor all being heightened.
Hayden Romero is a sophomore, and soccer player at Beacon Hills High School. She is genetically a chimera from a kidney transplant she had a few years previously. After being incubated by the Dread Doctors, she becomes a Chimera. Hayden is brought into the supernatural world through Scott's Pack and becomes the girlfriend of Liam Dunbar. Hayden is declared a failure and is killed by the Dread Doctors. Later, she is revived by Theo Raeken using the Soldier's blood to be part of his pack of Chimeras. Hayden rediscovers her humanity and leaves Theo for Scott's Pack so she can be with Liam. Hayden then completely loses her Chimera nature after willingly being bitten by Scott McCall, becoming a true supernatural beta werewolf.
As a Chimera, Hayden was a werewolf and werejaguar hybrid. She has the natural abilities and traits of both species. She has heightened enhanced speed and senses. Her werewolf half gives her the talent to take pain from others and pack symbiosis. Her werejaguar part is known to allow her to sense and track berserkers including the berserker Chimera Noah Patrick.
Tracy Stewart is a senior at Beacon Hills High School. She has chimerism due to her having an allogeniac skin graft. Tracy was the first Chimera in the Dread Doctors' newest experiment pool. When she became a Chimera, Tracy's transformations manifested to her as night terrors due her disorder. Eventually Tracy became psychologically locked away in her disorder from her being under the Dread Doctors' mind control, resulting in her having homicidal somnambulism. She went goes on a killing spree, including killing her own father, until she pukes up mercury, indicating she is a failure and she is killed. Tracy is then revived by Theo Raeken using the Soldier's blood to form his Chimera pack, and Tracy becomes his most loyal, and most ruthless combatant and right hand. Tracy is then killed by Theo to steal her power.
As a Chimera, Tracy is part werewolf and part kanima. In her transformation, she manifests the claws and fangs of a werewolf, has a wolf's instinct to follow her alpha and the symbiosis from being in a pack of canine werecreatures, but mainfests the hide, venom and the wall-crawling abilities of a kanima. Tracy has heightened strength, speed, agility and reflexes and an extremely heightened healing factor. Her abilities were the most potent in Theo's Chimera Pack. Her spark of power is stolen by Theo.
Josh Diaz is a junior at Beacon Hills High School. Josh was the fourth Chimera in the Dread Doctors' Beacon Hills' line of experiments. He is a carefree party-goer who drank and took drugs recreationally. The Dread Doctors' plan for Josh's corruption was to have him become feral. Josh became animalistically hungry for electricty, gnawwing on electric cables at the high school and Beacon Hills Hospital. When Josh is declared failure, he is killed by Theo Raeken at the Doctors' behest. Josh is then revived by Theo later with the Soldier's blood to be part of his pack to serve him as his alpha. Like Hayden and Corey, Josh rediscovers his humanity. Theo then kills Josh again to take Josh's electrical power.
Josh is part werewolf, like many of the other Chimeras, and part electric eel. He has the natural wolf instinct to run with a pack. His transformation consists of werewolf claws with overlarge front teeth. Josh has the power of electrokinesis from his electric eel makeup he can detect, absorb and weaponize electricity.