WARNING: The following article contains spoilers for the Season 15 premiere of Supernatural, which aired Thursday on The CW.
Across 14 seasons, Sam and Dean Winchester have faced the full catalogue of urban legends, supernatural monsters and biblical beasts -- from ghosts, to ghouls to gods. They've exorcised Knights of Hell; exterminated vampire nests and fought tooth and nail to cage the Devil. Dean even killed Death once. All in a day's work for the Winchesters.
But, even as they find themselves, in Season 15, tussling with the All Mighty himself in a bid to stop being "rats in a cage" on a cosmic level, there's something even worse lurking just around the corner for the boys. Something they've been neglecting since the end of Season 5.
After the release of all the spirits in Hell at the end of Season 14, Sam, Dean and Castiel try to contain the outbreak in the town nearest to ghost ground zero. They're joined by the body -- but not the mind or soul -- of Jack, possessed by a freshly released demon who offers his assistance on the grounds that he wants his cushy job in Hell back.
While alone with Dean, Demon Jack admits that he's something of a Dean fanboy, having "watched [him] work" when the eldest Winchester brother was condemned to the underworld in the Season 3 finale. During his time there, Dean's monstrous side was fully unleashed, taking up weapons of torture on the other souls trapped there with him. While he was following orders, there came a point where he began to reap a sick pleasure out of his terrible task, something he's tried desperately to forget.
Demon Jack not only reminds Dean of his darkest days in the nightmare realm, but is even complimentary of the hunter's artful technique. Though clearly uncomfortable, Dean asks the demon what Hell is like at the moment. The demon smiles. "You ever see an anthill when it's like, on fire?" He describes the moment at which God opened all the doors and, "boom, ta-da!" chaos reigned.
One word in particular gives Dean pause for concern. All the doors? Every single one? Demon Jack confirms the worst: Lucifer's Cage is open. "He wouldn't hold a grudge, right?" Demon Jack adds, a half-hearted assurance as the horrible realization seeps into Dean.
The Cage is a literal one, built to contain an archangel as powerful as the Devil indefinitely. At the climax of Season 5, Sam, possessed by Lucifer, and Adam Milligan -- Sam and Dean's half-brother -- possessed by the archangel Michael, fell into the Cage, putting a stop to the Apocalypse.
While Sam was rescued, Adam remained incarcerated -- out of sight and mind for a decade. When God's sister, The Darkness, was released in Season 11, Sam, Dean and Castiel were forced to come to Lucifer, who had also remained imprisoned, for help. Lucifer being Lucifer used the rare visit to escape. Adam and Michael were nowhere to be seen.
You can only imagine the toll that having one archangel rattling around in your head while another rattles around the confined space you're both entombed in takes on a person. Much less two archangels at war with each other -- one of whom is the root of all evil -- and that confined space is in Hell. And if all that wasn't enough, you've also watched your own brother be miraculously rescued while you're left to rot until what probably seems like the end of time.
Reminded of what an unspeakably horrible place his neglected half-brother has, from the sounds of it, just busted out of, Dean is starting to come to terms with the monster of his and Sam's unintentional making.
Airing Thursdays at 8 p.m. ET/PT on The CW, the final season of Supernatural stars Jensen Ackles, Jared Padalecki, Misha Collins, and Alexander Calvert.