Seth Gilliam as Alan Deaton -Druid-
Dr. Alan Deaton is the veterinarian at Beacon Hills Animal Hospital and Scott’s employer. Alan is like a father to Scott as his real father, Rafael, is deadbeat. During Season 1, Sheriff Stilinski goes to him for info when the murders are implied to be animal attacks. Alan, however, apparently knows more than he let’s on. In “Co-Captain”, after Scott is shot with a wolfsbane laced bullet by Kate Argent, Alan finds Scott and treats him revealing that aside from working with animals, he also works with werewolves, healing them when they are injured. In “Formality”, Alan remains calm and collected when Peter Hale, the Alpha werewolf arrives for Scott. Peter is repelled by the clinic’s balustrade is made of mountain ash. In Season 2, Alan helps Scott, Stiles, and Derek and his Pack against the Kanima. Alan is later visited by Ms Morrell, the school guidance counselor and French teacher, who confronts Alan over the wisdom of having Scott and his allies dealing with the current situation and “what’s coming”. Alan reveals to Derek that he had been a trusted adviser to the Hale family for a long time and that he made a promise to Derek’s mother that he would help Derek and look after him if anything were to happen to her. Alan helped Scott prepare the mountain ash laced pills to swap with Gerard’s cancer medication when Scott figured out Gerard’s plan to be Bitten by Derek. In the Season 2 finale, after Gerard’s plan fails, he and Morrell begin tracking him, Morrell saying she’s glad he’s out of retirement. It is revealed that the upcoming threat Alan and Morrell mentioned, was an Alpha Pack.
In Season 3, Alan has taken on a mentor-like figure to Scott and his friends, lending advice on the supernatural. In the episode “Unleashed”, Stiles comes to him concerning a new killer committing Human Sacrifices, having linked the murders to the Celtic Druids and that he always seems to have more information than anyone else. When Stiles demands why he’s always so cryptic and withdrawing, Alan alludes to have had a dark past that presumably caused him to go into retirement when he answers to have spent the past decade “trying to push something away” with the lies and the denial, that it could have a powerful effect on someone. When Lydia calls saying the music teacher has been taken for to be sacrificed he helps Stiles and Lydia identify the new killer as a Darach. He also identifies the pattern of the sacrifices of being groups of three offering the Darach its own type of power – Virgins, Healers, Philosophers, Warriors. It is discovered Marin is actually his younger sister, and that he and Marin are both Emissaries, Druid practitioners, that function as advisers to the werewolf Packs and ambassadors between them and humanity. Alan fulfilled this role for the Hale family, and was especially close to Derek’s mother, Talia Hale. In “Alpha Pact”, he helps Scott, Stiles and Allison find their parents, by proposing they take a sacrificial Druid ritual in order to locate the Nemeton which will have consequences for them, leaving a “scar” around their hearts for the rest of their lives and being substitute Guardian sacrifices for the parents which will fully revitalize the Nemeton, subsequently attracting the supernatural to Beacon Hills like a magnet. They decide to do it, to sacrifice themselves temporarily with someone to pull them back as a tether. Alan fulfilled this role for Scott. Later, Alan, with help from Cora and Lydia, saves the lives of the Alpha twins Ethan and Aiden when the Darach nearly killed them.
In the Season 4 premiere, “Anchors”, Scott and Stiles come to Alan concerning their and Allison’s psychological issues as a result of the Druid sacrifice. He informs them that when they died and subsequently resurrected, they essentially opened ‘a door’ in their minds which is still ajar. He tells them an opening into their minds is dangerous, that they each need to close that ‘door’. When it’s revealed the Nogitsune is possessing Stiles, Deaton heads to Japan in “Letharia Vulpina”, to retrieve a sample of a plant called letharia vulpina that was born out of the blood of the very Nogitsune Chris Argent saw killed 24 years earlier, which makes the plant “quite special”. Upon arriving back in Beacon Hills, he poisons Stiles with the plant which temporarily breaks the Nogitsune’s hold over Stiles. After Scott retrieves the Shugendō scroll in “Echo House”, which has instructions on how to exorcise a Nogitsune, Deaton translates that the host’s body has to be changed. In “The Divine Move”, Deaton confirms that the Hales’ triskele urn could imprison the Nogitsune’s essence because it was crafted by Deaton himself, out of wood of the Nemeton tree. At the conclusion of Season 3B, Deaton provides Scott counsel with the fallacy “Regression to the Mean”, saying things will stop being all bad, or all good and always revert to a neutral space. In Season 4, Alan helps to treat both Brett Talbot and Liam of being poisoned by yellow monkshood from being stabbed by the assassin Garrett. In “Weaponized”, Alan treats Reed a member of Satomi’s Pack, but he dies. Melissa later helps him perform an autonomy to learn what killed him. Alan identifies the cause of death as a weaponized variant of canine distemper as well as Satomi’s tea ritual, Wild Purple Reishi mushrooms as an antidote for the virus. In “A Promise to the Dead”, Deaton sets out to learn what Kate did to Derek, causing him to revert to being a teenager, and what it means for him. He visits Dr. Valack at the secret wing of Eichen House for supernatural inmates, from whom he receives a vision concerning La Iglesia. He figures out the old Mexican church is where Scott and Kira will be found after Kate abducts them.