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.
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.
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.
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 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.