Donovan Donati is a resident of Beacon Hills, California and a juvenile delinquent. He is a petty enemy of Sheriff Stilinski because of the Sheriff's history with Donovan's father. In Season 5, Donovan is one of the victims of the Dread Doctors, abducted, then experimented upon, becoming a Chimera. His Chimera traits consisted of a wendigo, as well as a lamprey. Donovan becomes a pawn for Theo Raeken so the latter can create dissent in Scott's Pack when Theo advises him to murder Stiles Stilinski if he wants to get back at Stilinski. Donovan carries out this act, attempting to kill Stiles but dies by accident when Stiles acts in self-defense.
Donovan is an extremely short-tempered young man, having very little ability to control his anger, being reckless, stubborn, immensely petty and psychotic. Due to his father being a cop, Donovan feels entitled in being one as well. He is totally irrational, directing his rage at Sheriff Stilinski for everything going wrong in his life and incessantly blaming the sheriff for his dad being confined to a wheelchair, making numerous threats to kill him. He takes any chance to bad-mouth anyone who gets on his nerve. After his conversion into a Chimera, Donovan's temperment is worse than ever, being totally unhinged, borderline psychopathic and impressionable as seen when he's easily manipulated by Theo Raeken. He quickly takes to the idea that he has superpowers now, showing passive interest and actually utilising control, then using them for his own gain and to harm others weaker than himself. He displays no emotional qualms in attempting to murder Stiles.
At some point in the past, Donovan's father was partnered with Deputy Stilinski. Donovan aspired to be a cop like his father.
When Donovan learned about his father's condition from a shooting, he rushed to Beacon hills hospital on his motorcycle, where he got into an accident that led to him being taken in an ambulance as well. Both men needed surgery, and Donovan received a skin graft to help with the healing of his wounds.
At some point after he graduated high school, Donovan applied for the police academy so he could become a deputy at the Beacon County sheriff station. But between the results of his anger expression inventory and his psychopathic deviant scale, it was determined that he wasn't a suitable applicant for law enforcement. It's likely that what happened to his father in conjunction with the realization that he would never follow in his father's footsteps by becoming a police officer was what ultimately led him to a life of crime. Donovana also harbored a grudge against Stilinski for what happened to his dad. He was arrested multiple times then was warned by a judge the next time he'd be arrested he'd be in prison.
Donovan is dragged into the sheriff's station by deputies Clark and Cordova, arrested for breaking and entering, and possession of a loaded .38 pistol. He tries to play innocent while struggling, repeatedly insisting the cops are making a mistake. Donovan hears Stilinski call out to him, and turns to face the sheriff.
Donovan instantly loses his temper at the sheriff's words and immediately starts screaming incessantly at Stilinski that he'll kill him while Clark and Cordova forcibly escort him to the holding cell.
Donovan: "Hey! Look at me. You're dead! Yeah! You hear that? You're going to do this to me?! You son of a bitch! You're dead! YOU'RE DEAD!!
A sulking Donovan is prepped for prison transport being cuffed at his hands and knees, then taken out of the station's cell by Deputies Clark and Parrish. Mr. Stewart, his attorney, briskly appears and accompanies them.
Mr. Stewart updates Donovan on his meeting with the District Attorney. The offer isn't what he'd hoped for, but still reasonable. Donovan asks what is reasonable, brusquely ignoring the deputies' insisting they talk in the van. Mr. Stewart acquises, telling him the DA wants Donovan for three to five years in prison, but reasons that a deal may be made to get him out in two instead.
Stiles snarks at Donovan's threat then sarcastically reassures him that he'll have plenty of time to "work on his performance while stuck in a tiny little cell." Donovan mockingly smiles at Stiles, then rushes at him, but is restrained by the deputies and they forcibly escort him out to the van. On the way to prison, Donovan fumes inside the prison transport van, guarded by an officer. Mr. Stewart snaps at Donovan that he'll be lucky to have him out in "three to five decades" after threatening Stilinski and his son in front of his entire department.
Later on, the driver begins to stiffen up and suddenly can't move. Donovan is disturbed as the van starts to dangerously twist and turn on the road. He then sees claws puncturing the roof of the van letting a thick viscuous liquid pour into the vehicle. The van sweers into a viaduct in the industrial estate.
After running for a while, still handcuffed, Donovan collapses in an alley, panting. The Dread Doctors suddenly appear in front of him. Donovan freaks out, terrified when the Doctors restrain him and yells out in pain when the para-scientists perform a lobotomy on him, drilling a device into his head. While Donovan screams in fear, his eyes become coated in a silver liquid. Once they are finished, the Doctors then have Donovan forget his entire encounter with them.
Donovan takes up hiding in a building, still out of his mind after seeing Tracy's attacking the van. He is then tracked down by Scott McCall and Donovan attempts to beat him, but the werewolf subdues him and he freezes.
The next day, Donovan is placed back in the station's holding cell. Sheriff Stilinski comes in to talk to him. The sheriff attempts to talk to Donovan about what he saw last night. He gently tells the young man that if anything he saw the previous night seemed peculiar, Stilinski will believe him. Donovan hides his obvious distress and snarkily mocks Stilinski thinking he's going to be accepting the Sheriff's help. He feels the effects from the Doctors' lobotomy, experiencing head pains and nausea.
At night, while he is still in holding, Donovan is listening to the sounds of the fight when Tracy attacks the station. Hearing the growls, he yells for someone to let him out. He is confused when he sees the lights flicker and hears peculiar supersonic and electrical sounds. The Dread Doctors come for Donovan, accessing the electronic key card reader to the cell and the door slides back. Donovan stares at them in confusion just before they whisk him out of the station undetected.
The Doctors ignore him with the Surgeon and the Pathologist holding him by the head. The Geneticist takes a pair of pliers, and she begins ripping Donovan's teeth out of his mouth, to the young man's total agony, spitting out blood. The Doctors eventually tear out all of his teeth. Donovan writhes in further anguish as new multiple rows of teeth appear sprouting out from his gums.
The Dread Doctors now complete their experimentation on Donovan, fully transforming him into their next Chimera after Tracy and Lucas. His Chimera traits include that of a wendigo and lamprey DNA. Donovan recuperates from the experimentation, still restrained to the examiner table, to his consternation. He hears footsteps and writhes against the restraints to no use.
Theo: "See, these guys, they believe in numbers and results. They'll weigh the pros and cons, they will decide and they'll decide fast."
Donovan: "Decide what?!"
Theo: "Whether or not you die."
Donovan grows increasingly agitated, whilst Theo shows him his psych evaluation from when he applied to be a deputy, defining it as multiphasic personality inventory. He gets under Donovan's skin by scolding him for scoring high on the psycopathic deviate scale. Donovan continues to angrily struggle while Theo continues to lecture him that his anger expression inventory declares him as "not suitable for law enforcement."
Theo then shows Donovan sympathy that he now can't be a cop like his dad. He then explains to him he now has power, including super-strength, speed and senses. Donovan perks up at this. Theo assumes Donovan will now want to use his new powers to hurt Stilinski in the most graphic way possible. Donovan now has given Theo his complete attention. Theo then suggests he'd like pulling Stilinski's teeth out, holding Donovan's chin, to his annoyance, but to Theo's amusement.
Theo: "The problem is though, sooner or later, physical pain ... it's manageable. See, real pain is emotional pain. That is the kind of pain that lasts. And if you want to cause Stilinski devastating, soul-crushing emotional pain, you don't go after him. You go after someone he loves."
Donovan listens to Theo's suggestion and completely swallows the Chimera's words, intending to cause Stilinski pain by killing Stiles. Overtime, Donovan adjusts to his new powers. Soon he's released from the Doctors' captivity and tracks down Stiles.
Donovan makes his way to the high school and comes up behind Stiles who's manning his Jeep. Donovan takes up his right hand and his palm morphs into a lamprey mouth with fangs. He slams his hand-mouth down on Stiles' shoulder, and Stiles yells out in pain.
Stiles runs into the high school while Donovan is several paces behind fully able to track him, his wendigo hunger and morphing lamprey mouths going out of control. Donovan follows Stiles' scent to the library. Stiles hides, but Donovan knows he's there.
Stiles' phone rings and Donovan taunts Stiles that it is Malia, asking him should he text her, his girlfriend, back. Donovan rants that Stiles doesn't even know who he is, asking him was he aware of the time back when their fathers were both deputies and partnered together. He tells the time of his father's injury from a shooting where he lost mobility in his legs because a shot severed his T-9 vertebrae.
Donovan doesn't stop his raving in that he blames Stilinski for his father's injury, insulting Stilinski for sitting in a police car and calling for backup instead whilst Deputy Donati was in action and got hurt. Donovan incessantly presumes that Stilinski left that part out to Stiles, branding Stilinski a coward while Donati went into action alone.
Donovan: " ... or do scared little bitches not tell their little bitch sons about their failures? About how they put their partner in a wheelchair for the rest of his life?"
Stiles keeps quiet and Donovan resumes searching for him.
Donovan snarls in anger, his teeth shifting into his fangs. Stiles climbs up the scaffolding trying to get away and the Chimera follows him up the levels. Shifting to his wendigo shape, Donovan scrambles up the scaffolding chasing Stiles and catches him by the leg.
Donovan: "Don't worry, Stiles. I'm not going to kill you." (Adopts his wendigo voice) "I'm just going to eat your legs."
Stiles desperately pulls and struggles against Donovan's grip, the psychotic Chimera not relenting.
The materials falls directly on top of Donovan, but right then one of the bars falls straight through him, impaling the Chimera through the chest. Donovan gasps and splutters, coughing up black ooze, gradually dying.
Stiles climbs down from the scaffolding in terror, while Donovan still looks at his prey with petty contempt, only the bar holding his body upwards. He gasps inaudibly leering at Stiles.
The young man attempts to pull the bar out of the Chimera's chest, but the motion proves futile as Donovan finally gives out, dying, with mercury oozing out of him.