Supernaturalkicked off its lucky 13th season on an emotional note, with Sam and Dean saying a heartbreaking farewell to Castiel -- along with all the other allies they've lost in recent months -- and reluctantly taking Lucifer's newborn son, Jack (who happens to be a full-grown dude) under their wing.

Luckily for fans, we already know that Cas is coming back this season, so we don't need to mourn Misha Collins' resilient angel -- but for the Winchesters, that loss is potent and, as far as they know, permanent.

"This profound sense of loss lingers over several episodes. He’s not coming back real soon, and it influences, greatly, Dean’s state of mind," says producer Brad Buckner, who was joined by his writing partner Eugenie Ross-Leming and star Jared Padalecki for a press conference to discuss the Season 13 premiere. "Both the guys have had to rebound from stuff over and over and just kind of shake it off and go on with the family business, and this overwhelming loss at the start of the season is something that Dean just can’t dig his way out of yet."

That grief is compounded by Dean's feeling that the Winchesters are truly alone in this fight -- as demonstrated by his desperate prayer to Chuck to bring back Cas and their mother, Mary, which once again went unanswered.

"It’s not only the loss of Cas, which is huge for the guys -- but especially for Dean, it’s another nail in the coffin about the loss of hope," agrees Ross-Leming. "He has to come up with a reason to have purpose; every battle, he feels like he’s swimming backwards ... You just feel that there’s a growing hopelessness and futility to his existence, and could lead to a certain kind of nihilism. I don’t think we’ll go thatnihilistic, but for him it’s a personal loss, but it’s also a cosmic loss of what’s the point of being here, when you scream at the wilderness and get nothing back?"

When Castiel does eventually return, Padalecki says that his unexpected resurrection will bring mixed emotions for the boys.

"There's obviously great relief. But there's also – and we'll see how it comes about – great concern about, wait a second, you saw us burn him. I don't know if we've had somebody come back after they've been salted and burned," he points out. "There's some genuine concern about what could have made this happen, who made this happen, why they made it happen. Can you trust it? Can you trust this version? When I came back, I was soulless. Is this different? There are a lot of questions in the air. Obviously, the major emotion is relief and happiness. But as is the case with all Supernatural, the other shoe might drop. So we'll see what happens."

Meanwhile, rumors of Mary Winchester's death have been greatly exaggerated -- she's currently stuck in an alternate universe with Lucifer, and with Jack's burgeoning powers still a mystery to him and the Winchesters, there's no clear way for them to get back to their timeline.

When Mary and Lucifer tumbled through the rip in reality, they were locked in a fight to the death, but right now Lucifer seems to have called a ceasefire.

"He knows a way he could make use of her. He's an opportunist, and he thinks there's a way he can use her to his own advantage," says Buckner.

"She's a pawn in his big-picture game," adds Ross-Leming. "The angels generally are middle management. They sort of do what they've been told; they're not policy makers, but Lucifer is a big picture guy, so he always has a plan... Mary's a piece of his puzzle."

The final minutes of the Season 13 premiere indicated that Dean is certain their mother is dead, while Sam "is not convinced," per Padalecki.

"Who knows if it's a sensation or a feeling he has, or it's just dumb hope, but there's another side to him and Jack, where Jack opened the rift once, maybe he is the only person who can open it again," he says. "I think Sam, the way he grieves, seems to be like 'okay, well, I'm going to try and focus on this, and get back to the rift, and see if Jack can do this, because I believe in him like people have believed in me,' and so we see Sam taking that route."

The producers hint that the alternate timeline will be a fixture in the show for much of Season 13 -- which will allow us to see some familiar faces who might be long dead in our timeline, like Jim Beaver's Bobby, who we saw in the Season 12 finale. "Ultimately, this world becomes yet another threat that gets built to in the course of the season. So that’s been a lot of fun," says Buckner.

But while Mary and Lucifer (and hopefully some old friends) are dealing with the drama of the alternate timeline, Sam and Dean have to deal with the more pressing concern of what to do with Jack.

His inclusion allows the show to reinvent itself once again, with a villain who might not be a villain at all; an examination of morality that could test everything Sam and Dean believe; and an opportunity to see how the Winchesters' parenting styles differ.

"I think Sam relates to him in lots of ways, that person who doesn’t quite belong, the person who has been left, abandoned. So I think there’s already that kind of psychological bonding going on," says Buckner. "Dean’s going to take a while. Sam I think comes at any problem more from scientific method. He examines the evidence, and if the evidence leads you to one conclusion, then that seems sort of obvious. And Dean operates off of his gut, and what his gut is telling him is this is the spawn of Satan. And I don’t know if that kind of character has ever been presented in a favorable light. We’re conditioned to that Omenkind of thing, and this kid has got qualities that while he obviously can be potentially dangerous, he is curious and inquisitive and willing to believe, and that Sam takes as adding up those positives. So he becomes a parent first. Dean is more slow to come around and is determined to get rid of this problem."

"I mean, Dean has been a parent all his life. He’s parented Sam. They’re children of abandonment, so Dean has a lot of practice in being a parent and not as much practice in being a child. That’s a huge hole in him, his never having been nurtured that properly himself," Ross-Leming adds. "But I think with the arrival of Jack we are dealing now with, yes, he’s the son of Satan, but he’s also the son of humanity. We don’t actually know ourselves -- although there’s arguments about this -- where he’s going to go in terms of what his destiny is. But what that has led us as writers to do is to start redefining what is good and evil anyway? I think this season will be a little more nuanced."

Supernaturalairs Thursdays at 8 p.m. on The CW.