Donovan Donati is a resident of Beacon Hills, California and a juvenile delinquent. He is a petty enemy of Sheriff Noah Stilinski due to blaming the Sheriff for Donovan's father's paralysis. In Season 5, Donovan is abducted by the Dread Doctors, then converted into a Chimera. His Chimera traits consisted of a wendigo and a lamprey. Donovan becomes a pawn for Theo Raeken so the latter can cause dissent in Scott's Pack when Theo advises him to murder Stiles Stilinski if he wants to cause Stilinski pain. Donovan carries out this act, attempting to kill Stiles but Stiles accidentally kills him in self-defense.
Donovan is an extremely short-tempered man, having very little ability to control his anger. He is reckless, stubborn, immensely rude to authority figures and borderline psychotic. Due to his father being a cop, Donovan feels entitled in being one as well. He is extremely petty and 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 transformation into a Chimera, Donovan's temperament becomes worse than ever, being totally unhinged, borderline psychopathic and very impressionable as he was 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 causing harm to 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 could never follow in his father's footsteps 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 handgun. He tries to play himself off as innocent. Donovan hears Stilinski call out to him, and turns to face the sheriff. An annoyed Stilinski reprimands Donovan for forgetting the judge's warning that the next time he ran afoul of the law, he'd do time in jail. Donovan begs Stilinski to let him go, trying to reason with him, but Clark informs Stilinski about his felony and the gun.
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!!
Mr. Stewart updates Donovan on his meeting with the DA. The offer isn't what he'd hoped for, but still reasonable. Donovan asks for more information, brusquely ignoring the deputies' insisting they talk in the van. Mr. Stewart talks everyone down then acquiesces, telling him they wants Donovan to serve three to five years in prison, but reasons that a deal could still 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. 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.
Mr. Stewart sees a girl outside the van, calling her by name Tracy, his daughter. Tracy then attacks the van, mortally wounding the driver. Donovan, Mr. Stewart and the officer are instantly disbelieving, horrified and terror stricken. Tracy savages the vehicle, but Donovan manages to escape out the back of the van and runs up out the viaduct and into the streets.
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 tackle him, but the werewolf subdues him and he freezes.
Donovan continues to feels the effects from the Doctors' procedure, experiencing head pains and nausea and mercury covering his eyes.
Donovan is held inside the Doctors' operating theatre, strapped to a examination table. Totally confused, Donovan struggles against his restraints to no use. The Doctors then appear and take turns examining him, to his distress. The Surgeon notes "(Donovan's) condition looks promising." Donovan, confused, yells at them asking what they are talking about.
The Dread Doctors now complete their experimenting on Donovan, fully transforming him into their next Chimera after Tracy and Lucas. He recuperates from the conversion, 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: "The problem is though, sooner or later, physical pain it's ... 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 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's Malia, asking him should he text her, his girlfriend, back.
Donovan doesn't stop his raving that he blames Stilinski for his father's injury, bad-mouthing him for sitting in a police car and calling for backup 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 his father 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.
He finds Stiles who's rested against a bookshelf and pulls Stiles out through the shelf. Donovan then slams the young man against the construction scaffolding. Stiles recovers and elbows Donovan's face, knocking him backwards.
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 then looks up, then reaches for and pulls a pin holding construction materials up on the upper level. Pulling the pin out, Stiles releases the materials, including metal bars on top of the delinquent in an attempt to knock Donovan off his balance.
Stiles attempts to pull the bar out of the Chimera's chest, but the motion proves futile as Donovan finally gives out, completely dead, with mercury oozing out of him.
Donovan's body remained in the library while Stiles has a panic attack over having killed someone. After Stiles and Theo leaves, Deputy Jordan Parrish, an unconsciously acting hellhound retrieved Donovan's corpse and cleans up the scene. The hellhound then brings the body to the Nemeton as part of his mission to hide his supernatural features. Parrish burns Donovan's body remove his Chimera traits.
Donovan's corpse is last seen in the morgue, his supernatural attributes cleansed, studied by the sheriff and Stiles where Noah helps his son forgive himself for Donovan's death.