Writing an end to any long-running series is no small feat, but for the CW’s “Supernatural,” the task seems Herculean.

The monster of the week-turned-demon-hunting drama is embarking upon its 15th season, which also happens to be its final one, after surviving the merger of its original network WB with UPN to form its new home, the CW, as well as outlasting multiple network presidents and showrunners. On the content side, its lead characters of Dean and Sam Winchester (Jensen Ackles and Jared Padalecki, respectively) have battled everything from vampires to shapeshifters to Lucifer (Mark Pellegrino) and now God himself (aka Chuck, played by Rob Benedict). Needless to say, there are a lot of loose ends to tie up, and a definitive end to write, before the screen goes black on its 20th episode. But to ask the writers and producers of the show, it is just business as usual as they put together a season of demon-hunting, ghost-hunting and God-hunting.

“I don’t know that our approach this year has been that much more different than last year, other than we’re writing to an ending, rather than a cliffhanger,” executive producer Andrew Dabb tells Variety. “The temptation is that you’d go into a final season and just do straight serialization with every episode tying to the bigger, larger God plotline, and we do have a lot of episodes that do that, but it still needs to feel like a season of ‘Supernatural.’ So there are a lot of standalone adventures — some are scary, some are funny. We wanted to keep that mix going because it’s a key part to the show overall.”

When Season 15 begins, with a premiere episode entitled “Back and to the Future,” the immediate action is in seeing Dean and Sam deal with literally being surrounded by dozens of beings that had previously been killed or otherwise vanquished, but which were returned to Earth when God aka Chuck (Rob Benedict) got angry at the end of Season 14. This direct conflict will be something the guys have to deal with into the second episode, but the repercussions of having so many dangers back in the world will “reverberate throughout our entire season,” Dabb says.

“When God is your uber-villain, it’s not just a one-episode deal,” adds executive producer Bob Singer. “It’s not simple, just going for Chuck, and a big part of what we’re dealing with in the season is how to do that. At a certain point, Chuck will be at full strength, which gives our boys even more problems.”

This also will allow the show to return to some of its roots in the conversation around free will, which, Dabb points out, “has been largely an illusion, so the question is, how do they reclaim it really for the first time?” The final season of “Supernatural,” he adds, “will go to greath lengths to address” whether free will is really even possible as long as God is in the picture.

But first, another immediate issue to work through is Jack’s (Alexander Calvert) death — an event that left him in a black void at the end of the previous season — and the guilt the various men, specifically Castiel (Misha Collins) feels around that event. At the outset of the season, the “Supernatural” foursome of Dean, Sam, Castiel and Jack are split up, but Dabb notes they won’t be for long because “ultimately this is a found family, and they have deep emotional bonds” that make up the most important part of the show.

“This is not just true of this season, this has been true for awhile, but we can devote a lot more time to the emotions of the guys,” Dabb says. “In the beginning of the show they were always on the road, but since they’ve been able to be settled, we’ve been able to see their lives beyond just the next monster.”

In the beginning of “Supernatural,” the format was a monster of the week roadtrip show that followed brothers Dean and Sam around the country in their 1967 Chevy Impala “saving people, hunting things” as they also searched for their father, who had disappeared while on a hunt of his own. The early days of the show saw it on the renewal-cancellation bubble, but it gradually picked up steam — and viewers — and has now become the longest-running genre broadcast series, hitting 15 seasons and 327 episodes before it signs off in the spring of 2020.

“I think you really get an evolution of TV as a medium. When this show started it was a very different show than where it will end, and the same thing about television generally. And I think what’s allowed the show to stay on as long as it has is that it’s been able to adapt,” Dabb says.

Production on the final season is still ongoing, which Singer admits means it’s still a bit too early to pick their heads up from the work to really reflect on the show’s legacy. But, one integral element he already is eager to tout is how the show managed to run as long as it did “maintaining a high quality and keeping our core audience loyal to us. I think that’s a pretty special accomplishment and that’s probably what I’ll take away more than anything,” he says.

And despite the fact that the team behind the show has expressed willingness to have conversations about returning to these characters and this world down the line, Dabb, Singer and their writers’ room was not concerned with what ifs. “We weren’t really considering whether there would be a future movie or a reboot or anything like that. We wanted to write the best ending that we could, that we all were internally happy with, and that’s what we’ve done,” says Singer.

In part, this includes the return of many familiar faces from past seasons, such as reaper Billie (Lisa Berry), hunter Eileen (Shoshannah Stern), prophet Kevin (Osric Chau) and half-brother Adam (Jake Abel). “I think we’d be promising more than we could deliver if we said we would tie up every loose thread the show has dropped over 15 seasons, but we’re going to tie up the big ones,” Dabb says.

“I hope we’re speaking to the majority of our fans. There’s definitely episodes where we do address things that come out of the fandom and out of social media, but in terms of how the story ends, in terms of bringing back certain characters, it was [about] what makes sense for the guys on their journey and in this story at this point. To some extent, all television now is fan service, but it’s not about direct fan service in that way; it’s more about what is going to get us to the emotional conclusion that we want for these guys.”

The final season of “Supernatural” premieres Oct. 10 on the CW.