Styne Family Massacre

The Styne Family Massacre was the massacre of the American branch of the Styne Family by hunter Dean Winchester in revenge for the murder of Charlie Bradbury.

Background
For over a thousand years the Styne Family sowed chaos and destruction in order to profit from it. They also used genetic engineering and biological enhancements to make themselves stronger, more durable and harder to kill. Originally known as the House of Frankenstein, their secrets were discovered by author Mary Shelly who's Frankenstein books forced them underground with the new name of Styne. Continuing their work, the Styne's were facilitated by the Book of the Damned but lost it around the 1930s and it ended up in a monastery crypt in Spain which was eventually destroyed. However, the Styne Family were not crippled by the loss of the Book and continued with their destructive acts.

In 2015, Charlie Bradbury rediscovered the Book of the Damned while trying to find a cure for the Mark of Cain for Dean Winchester and the Stynes, led by Jacob Frankenstein, began hunting her in hopes of getting it back for themselves. Jacob and his men were killed by Charlie and the Winchesters, but Sam only pretended to destroy the Book, seeing it as the only chance to remove the Mark of Cain from Dean's arm. A few weeks later, the Winchesters and Charlie came into contact with the Stynes again after discovering a murder committed by Eldon Frankenstein in order to harvest a girl's eyeballs. After capturing Eldon, the Winchesters learned of the family's history but Eldon escaped and went after Charlie who had managed to decrypt Nadia's Codex, the key to reading the Book of the Damned. Charlie emailed her notes to Sam and destroyed her computer before being murdered by Eldon. Enraged by Charlie's murder, Dean decides to hunt down and destroy the Styne Family in revenge.

Battle
To start hunting down the Stynes, Dean returns to the Blackbird Motel where Charlie was murdered and gets security camera footage of the vehicle belonging to the killers. Dean then contacts fellow hunter Rudy and asks him to run the license plate on the vehicle. Rudy tells him that it belongs to Eldon Styne of Shreveport, Louisiana but there is no street address. Dodging Rudy's questions about Sam, Dean departs for Shreveport.

In Shreveport, Dean is pulled over by the local sheriff and a deputy who smash out the Impala's taillights and use it as an excuse to arrest him. While questioning Dean, the deputy mentions someone telling him about Dean and Dean overpowers the deputy and escapes. Taking the deputy's gun, Dean confronts the sheriff as he gets off a call with Monroe Frankenstein, telling Monroe that he has Dean. Dean hits the sheriff twice and demands to know who he was talking to. After learning that it was Monroe and that Monroe is Eldon's father, Dean demands the location of the Stynes. The sheriff tells Dean that the Stynes own the town and are like gods around there, but Dean states that he kills gods and asks again. The sheriff eventually gives up the location of the Styne home to Dean.

Entering the grounds of the Styne home, Dean equips his pistol with a silencer and kills a guard by stabbing him in the neck. Outside the front door, Dean takes a second guard hostage until a third turns around. Dean then kills the third guard with a shot to the head and the second with two point-blank shots into his back. Arming himself with both his pistol and the second guard's gun, Dean enters the house where he is surrounded by over a dozen armed family members. As Monroe greets Dean, Eli puts a plastic bag over Dean's head and suffocates him unconscious.

Dean wakes up on the operating table in the Stynes lab where they plan to take him apart for pieces for themselves. Monroe is amused that Dean believed he could come in "guns blazing" and win. Dean warns them that if they kill him, he will be resurrected as a demon by the Mark of Cain and if they let him go, he might or might not let a few of them live, but at least he will be human. The Stynes are undaunted, seeing a man that doesn't die as the perfect lab rat. As Monroe goes to cut him open, Dean breaks free of his restraints, cuts Eli's throat with a bone knife and overpowers a nurse, killing her with a lethal injection she attempts to use on him. Dean then grabs Monroe and begins strangling him, informing Monroe that he took something from Dean who will take everything from him in return. Monroe gasps out that its too late as Dean's family and home will be gone before Dean snaps his neck. Taking Monroe's gun, Dean heads out into the house and brutally slaughters everyone he finds there, over a dozen people.

Dean returns to the Men of Letters bunker where Eldon, Roscoe and Cyrus are collecting everything they can find that's useable with the intention to burn the rest. As Eldon prepares to light a pile of books on fire, Dean stabs Roscoe through the spine with a knife and he enters the bunker's main room and collapses dead before Eldon and Cyrus moments later. Eldon taunts Dean over Charlie's murder and believes that he can defeat Dean now with the new arm his father gave him after he ripped off his old one to escape the bunker. Dean tells Eldon that he killed Eldon's father and all the rest of his family. Dean then notes that while Eldon has two hearts and several other extra organs, he only has one brain. Not understanding, Eldon asks "so" moments before Dean pulls out his gun and shoots Eldon in the head, killing him.

With Eldon dead, Dean turns his gun on Cyrus who begs Dean not to kill him, telling Dean that he's not like the rest of his family and he hates them. Cyrus displays his lack of enhancements as proof but Dean feels that even if Cyrus isn't evil now, he has evil in his blood and it will eventually consume him. Cyrus pleads that he will do anything Dean wants and he doesn't need to kill him. Dean appears to agree for a moment then tells Cyrus that he does have to. Dean shoots Cyrus through the head, killing him.

Aftermath
Moments after Dean kills Cyrus he is found by Castiel who is horrified by Cyrus' murder, especially as the Dean he knew would never have killed Cyrus. Castiel attempts to stop Dean, who is falling further and further under the Mark of Cain's influence from leaving, but Dean fights back and very nearly kills Castiel before he stops himself.