The end of Supernatural is in sight but there are a bunker full of plot threads and character arcs still in need of resolution in season 15. Supernatural has enjoyed unprecedented longevity since first airing in 2005 and a major part of that success has involved constantly introducing intriguing new characters and engrossing new stories, as well as expansive new pieces of lore for Sam Winchester to check. It's only natural that after fourteen years in business, and with the real-life issues of actors, writers and TV studios to deal with, not everything in the world of Supernatural has been neatly rounded off.

Certain character arcs still need to be completed, some mysteries still require an explanation and, of course, the overall story of the Winchester brothers needs to reach a full and satisfying conclusion. However, Supernatural won't have much longer in order to do that, as the forthcoming season 15 is now confirmed to be the show's final stand.

Related: How Supernatural's Original Five-Season Plan Ended

Following on from the season 14 finale, Supernatural's last ride will primarily focus on the heroes' attempts to avoid another apocalypse, after God rose Hell's souls to walk the Earth again. If the boys manage to handle that situation, there's also the small matters of God himself and the increasing fragile state of heaven to address. Aside from those major final season plot points, plenty of other stories from the blood-soaked Supernatural canon also remain in need of resolution.

Supernatural Character Arcs That Need A Conclusion

Supernatural season premiere final scene Mary and Lucifer

Sam and Dean have always put family first, often putting the world itself in peril as a result. The Winchesters have also adopted many others into their family, such as Castiel, Charlie and Jack. Consequently, viewers might have expected Sam and Dean to welcome their half-brother, Adam, with open arms when he first appeared during season 4, but instead they've left him in Hell for ten years. Used as a vessel for the archangel Michael, Adam was consigned to Hell's Cage and has only been mentioned in passing since. With God opening the floodgates of the afterlife, Adam may well return in Supernatural season 15, but it could be too late for the Winchesters to save him.

Played by Samantha Smith, Mary Winchester was resurrected in season 11 and has been a main member of the Supernatural cast ever since, hunting alongside her two sons. However, Mary's story came to an abrupt conclusion last season, as an increasingly erratic and overpowered Jack accidentally killed her during an argument. This moment arrived so suddenly that Mary's story still feels somewhat incomplete and there needs to be some resolution with both her biological sons and the adopted son who inadvertently caused her demise.

Recurring villain, Lucifer, suffered a similarly uneventful final appearance. Powered by Michael, Dean finally managed to kill Lucifer in the season 13 finale, sending the Devil to a place called "The Empty" where angels reside after death. Lucifer's ex-vessel, Nick, came close to resurrecting Satan but was ultimately foiled by Jack. As Supernatural's foremost baddie, it would be strange for Lucifer's final scene to be as a formless CGI shadow with red eyes, and with Jack now also residing in the Empty, Mark Pellegrino's Lucifer could be set to return alongside his on-screen son for Supernatural's final season.

Related: Why Vampire Benny Should Return For Supernatural's Final Season

Supernatural Stories That Remain Unresolved

Shedim in Supernatural

Any season of Supernatural is arguably only as good as its monsters, and season 13 seemed to have something big planned when the demon ruler, Asmodeus, began a plan to unleash the Shedim. Lucifer himself was said to be afraid of these mysterious beings, but all the audience saw of the Shedim was an arm rising out of the ground, before the summoning was interrupted and never spoken of again. The Shedim were said to dwell in a special section of Hell and, once again, may have been freed by God's villain turn in the season 14 finale.

Supernatural season 5 introduced a young, innocent-looking boy named Jesse Turner, who just so happened to be the Antichrist. Jesse held incredible demonic powers and shared a strong link with Lucifer, but after voluntarily exiling himself, Jesse has yet to return to the series. In many ways, Jesse was a prototype version of Jack, albeit without the nephilim body, and it's not known whether his powers have grown due to Lucifer's power-ups or diminished after the Devil's death.

An early hallmark of Sam Winchester's character was demonic psychic powers that he shared with others dotted around the world. This story was dropped as soon as it became clear that Sam's abilities would make hunting monsters a 5-minute job but, in theory, Sam's powers still lay dormant within him. Since Supernatural no longer has to worry about the future, the writers can make Sam and Dean as powerful as they please, meaning these abilities could resurface in season 15.

Predictably, quite a few Supernatural villains have fallen off the radar over the years. Season 7, for example, introduced the powerful Leviathans and although Sam and Dean were able to defeat their leader, business mogul Dick Roman, the fate of the remaining Leviathans has gone unexplored. It's strange that the Winchesters haven't encountered these beasts again, and the same could also be said for Famine, War and Pestilence. While Death has been a recurring figure, the other Horsemen have been absent after Sam and Dean defeated them in season 5 and took away their rings. The trio were left weakened, but with the current whereabouts of the rings a mystery, the Horsemen could be set for a revival and return with a score to settle in season 15.

Related: Every Previous Adventure Referenced In Supernatural's 300th Episode

Ending Sam And Dean's Supernatural Story

Jared-Padalecki-as-Sam-Winchester-and-Jensen-Ackles-as-Dean-in-Supernatural

The success, or otherwise, of Supernatural's final season largely rests on how Sam and Dean's tale is brought to a close. Back in season 13, Billie (now promoted to the lofty position of Death) told Dean that although she wanted to reap him, the Winchester family still had work to do. This vague statement could apply to a variety of feats the Winchesters have accomplished since then, but after Billie's brief cameo in the season 14 finale, it seems likely that the exact nature of Sam and Dean's task is yet to be revealed.

Sam and Dean have often been forced to give "the talk" to members of the public unfamiliar with the paranormal, but season 14 floated the idea that the brothers should share this information with the entire world. While Dean was characteristically opposed to this suggestion, Sam seemed a little more amenable, and this could set up a potential ending for Supernatural, where the Winchesters retire and leave the fate of Earth in the hands of the people.

When all else is said and done, the biggest question Supernatural must resolve is how the Winchester brothers bow out. Do they die in a blaze of glory, live happily ever after, or keep on trucking in the hunter lifestyle just as they always have done? To reach a conclusion, Supernatural must address perhaps the longest running plot thread in the show: Sam and Dean's growing disillusionment with the hunter's life. With each passing season, each battle, and each loss, the Winchesters have become increasingly jaded and tired with the constant fight they must endure. In season 13, Dean even asked Billie to reap him, seemingly preferring the release of death over the prospect of returning to the mortal plane and continuing the ongoing war against the paranormal. In earlier seasons, the brothers harbored hopes of a happy ending, but those dreams have now been forgotten and Supernatural season 15 needs to provide an end point for this emotional journey.

More: Why Supernatural Has Been Cancelled After 15 Seasons

Supernatural season 15 premieres October 10th on The CW.