Cerberus is an ancient, eternal Hellhound, an extraordinary fire-based supernatural being and an anti-hero who is tasked with covering up the supernatural from humans. He was also destined to battle against the Beast of Gevaudan, a destiny he fulfilled in the fifth season.
It is unknown if there is only one Hellhound, or if there are more; the fact that Cerberus has had so many name throughout history seems to indicate the former, or at the very least, that there are very few. If it is the latter, then Cerberus is at least one of the most well-known Hellhounds, and presumably is the longest-lived as well, given that his namesake originated in Ancient Greece around the 8th century BC. Ironically, despite battling Chimeras throughout Season 5 in Teen Wolf, the mythological Cerberus had a Chimera for a brother, with the other two being a Hydra and Orthrus, a two-headed dog.
Cerberus has gone by many names throughout its immensely long life, including Garmr, the Black Shuck, and the Black Dog, presumably gaining the names from various different cultures' version of the Hellhound legend in mythology. However, it appears that these are all simply different names for the same eternal Hellhound spirit. From the short amount of time the Hellhound has been seen in control of Parrish's body, he has given the impression of being aloof and focused solely on fulfilling his mission, barely seeming to notice anyone or anything else around him due to his view that it is small and unimportant in comparison to the work he must do. However, he is perfectly willing to eliminate any obstacle in his path if they seem to get in his way, such as the violence he has committed in his pursuit to take the bodies of the dead Chimeras to the Nemeton.
That said, he tolerated Scott and Liam's presence, allowing them to follow him in his pursuit of the Banshee, Lydia Martin, at Eichen House; he even moved Stiles out of the way with only minimal force so he could shield them from the force of the Banshee's scream. This contrasts strongly with his reaction to the members of the Chimera Pack, who he forcefully attacked after Theo Raeken ordered them to take him down. The Hellhound even warned Scott and his pack about the Beast's trap, suggesting that he at the very least views them as innocent lives who are not worth killing, or as possible assets to aid him as they share the same goal, finding the Beast. However, their method of dealing with the Beast likely differs from his own.
Cerberus also spoke as himself for the first time when telling the pack of the Beast's trap, something he rarely does as he usually doesn't care to interact with others. As a result, he typically gives Jordan Parrish control over his body during the day, allowing him to live his day-to-day life while only taking control for himself after nightfall. After Lydia's desperate plea to Cerberus in A Credible Threat, the Hellhound seemingly merged with Parrish, allowing them both to work in tandem by giving Parrish control of his powers rather than wresting his body from him at night.
Personality wise, Cerberus is seemingly completely neutral and thus neither good nor evil. He views Parrish as nothing more than a vessel in his mission to defeat the Beast, but he was willing to listen to Lydia when she told him that he could only defeat his foe by accepting Parrish's spirit and allowing them to work together, which ultimately led them to succeed in their battle against the Beast. While his duty is to cover up the supernatural, he hasn't attempted to kill witnesses nor those who know about the supernatural, suggesting that he has some sort of moral code regarding loss of innocent life. He ignored the deputies when they raised their weapons against him, either because he viewed them as no threat or as frightened misguided mortals not knowing what they were dealing with, however, Stiles did tell them to let Cerberus/Parrish go without shooting at him, so it is unknown what would have happened had Stiles not intervened. Cerberus has used aggressive force against the deputies when they were guarding the morgue, though he did go out of his way to use non-lethal means and even impersonated Parrish to get the Sheriff to leave.
As an amortal and infinite being, he views the mortal world with an emotional distance, having no real use or care for it, which is demonstrated by his frequent burning of public property or walking around naked or semi-naked as a result of his powers. The latter is somewhat ironic, as he is supposedly on earth to cover up the supernatural, but he unwittingly draws attention to himself due to his inability to care about public reaction. That said, the attention drawn is only down to his lack of clothes (which are usually burned away by his Hellhound fire) as he doesn't ignite his flames unless in the presence of other supernaturals or Chimeras.
Powers and Abilities
Cerberus is a Hellhound and possesses the powers and abilities that come with being such a creature. However, due to his immense age, Cerberus likely has greater experience than most other supernatural creatures, and as a result is patient when dealing with inferior beings. When facing threats that are beneath him such as the Chimeras, Cerberus allowed them to make the first move, only giving off an expression of both amusement and exasperation when they attacked him. Cerberus is also the only known creature that survived multiple encounters with the Beast of Gevaudan in one-on-one fights and was able to fight back almost evenly before ultimately losing as a result of the internal struggle between him and his vessel, Jordan Parrish. After merging with Parrish, Cerberus/Parrish showed strength equal or possibly greater than the Beast as when they were in a grapple with The Beast, Cerberus/Parrish was able push down the Beast's arm with only one hand but ultimately failed in overpowering the Beast due to Lydia's scream distracting him.
According to Cerberus, he is beyond life and death and are one of the few (if not the only) infinite beings in the Teen Wolf universe. He implied that his spirit is extremely old, and judging by the comment he made about being known as Cerberus, a Hellhound figure from Ancient Greek mythology, he has possibly existed for at least a millennia. While the human vessels of the Hellhound may perish in time, the Hellhound spirit itself exists forever by being reborn into new human bodies when he has a supernatural duty to fulfill on Earth.
Cerberus is incredibly strong. This was demonstrated when Parrish knocked Theo Raeken out with one punch and flipped over Stiles' Jeep with ease while Stiles was still inside of it. It even had enough strength to possibly rival The Beast by blocking its strong strikes, though he had to this with two hands due to the immense size difference between them. After accepting his vessel and thus no longer having a "internal conflict", Cerberus' strength increased to the point he was able to get into a grapple with the Beast and show slightly greater strength than the Beast.
Cerberus is bound to the body of a human when he has a duty to fulfill, and while he is possessing a human, he seems to only be partially active, as he is suppressed within human form for most of the daytime hours, allowing the human vessel to go about their day-to-day life. Additionally, Cerberus is more vulnerable during the daylight hours, as it usually isn't until after nightfall that he takes his Hellhound form. Fire is currently the only known thing that can reliably force the transformation from human to Hellhound so as to counter this weakness. Because of their dual nature, the behavior of the human vessel while in Hellhound-mode can be unpredictable, and is said to be why Cerberus was losing his battle against the Beast, since he and Jordan Parrish were constantly fighting each other for control. However, it seems that it is possible for the Hellhound and their vessel to completely merge together, allowing the human access to the Hellhound's powers at will, though they will still be more powerful at night and weaker during the day. This appears to be the case with Cerberus and Parrish, who now seem to be working in tandem rather than fighting each other for control.
Should Cerberus take too much physical damage such as impalement through the chest or enduring the powerful attacks of the Beast, he will revert to back to Parrish. Fire can counter this weakness by summoning Cerberus back into control, as evidenced when Scott and Liam sprayed at Parrish with a makeshift flamethrower to summon Cerberus, as they needed his help in locating Lydia Martin in Eichen House.
- Cerberus is the second spirit to be inadvertently summoned or released by the McCall Pack, as it was Allison Argent, Scott McCall, and Stiles Stilinski's surrogate sacrifice ritual in Season 3A's Alpha Pact that allowed him to be reborn. The first was the Nogitsune, who had been imprisoned under the Nemeton and who was released by a combination of the surrogate sacrifice ritual and the collapse of the Nemeton's root cellar caused by Jennifer Blake's geokinesis.
- With the Beast defeated, Cerberus fulfilled his part in the battle prophesied in the painting, as he was instrumental in the Beast's downfall with the help of the McCall Pack.
- Cerberus possessed Jordan Parrish at the exact moment that he was blown up in a IED attack while serving in the US Army on deployment in Afghanistan.
- Tracy Stewart was the only Chimera not to fear Cerberus, as both Corey and Josh was reluctant to go up against him and Theo used Lydia as a shield, while Tracy was the first to charge against the Hellhound.