With The 100's now-healed Roan (Zach McGowan) the leader of the thirteen clans—and the apocalypse nigh with the remaining nuclear reactors breaking down, giving humanity about six months to live—new alliances will be formed, old friendships will be revisited, and true colors will be revealed.

On the show's Vancouver set, the cast shared tidbits about what's ahead in Season 4.

Roan and Clarke forge an unexpected partnership

In the aftermath of Roan's new power—and Clarke (Eliza Taylor) giving him the flame—the duo have an "unlikely relationship," McGowan admitted. "They have some sort of respect for each other even though they've always been pointing weapons at each other or dragging—I did a lot of dragging her through the woods tied up last season," he said. "I think their relationship plays heavily into what happens, as well as some of the other people from his part that kind of pop up as well."

Taylor acknowledged viewers "are going to see them definitely kind of team up a bit." "Last year I was like, 'This has created an interesting dynamic that wasn't on paper,' which I love," she said. "I think they've really kind of seen that and taken it into the next season, which is great."

What happens now that many of the core group know mankind's existence could be wiped out in six months?

"I think that's a big theme of this season is seeing everyone's true colors when all the chips are on the table," said Richard Harmon, who plays Murphy. "This is coming. It doesn't really look like there's any way we're going to be able to get around it. It's probably going to kill us all. What do [they] do with that information?"

"We all have to figure out how to address that and whether you decide to find a way to get through it or find solutions to live through it or whether you start making a bucket list and just decide to let it wash over you in a literal sense," Bob Morley, who stars as Bellamy, added. "There's that existential dilemma of whether we deserve to survive or whether should we live the rest of our lives hedonistically with whatever we have left. That's definitely the clock that is ticking throughout the season."

With that timeline looming over the characters, it proves "a catalyst to putting these groups together," Morley said. "There's a whole heap of different groups that you won't usually see and I think the writing team really likes to explore putting characters together that you wouldn't expect together."

And Indra (Adina Porter) will find herself in one of those situations. "Split-second alliances happen when the world is coming to an end," she teased. "We make split-second judgment calls about who you can trust…You've always seen Indra being the brave warrior, but sometimes you can fight your way to survival, and sometimes you’ve got to figure out new skills to survive. You'll see…some new skills."

The show will explore the past—again

The 100 will once again explore life prior to the series in an upcoming episode. "There [are] some flashbacks actually," Marie Avgeropoulos (Octavia) teased. In addition to the return of at least one deceased character, "you're going to get to see a lot of the characters and how they interacted with one another."

The "old crew" is back again

With a large cast—and storylines that often keep characters apart for extended periods of time—Season 4 finds Clarke "relying on her friends and family," Taylor previewed. "Which is good because a) Eliza missed working with them; and b) it's kind of like the old crew being back together again. It feels like Season 1 again, which is awesome."

One of Clarke's allies? Bellamy. "I think they're on the same team again, which is really cool and you saw that at the end of Season 3," Taylor said. "I really like the way their storyline is going. There's a lot of mutual respect and they're sharing the leadership role, so that's cool."

Also, "there's a return of the adventure squad of the younger kids as well, which is a lot of fun," Morley teased. And fans will see "a lot of Bellamy and Kane's relationship which is really great for me. I love working with [Henry] Ian [Cusick]. We have a lot of fun."

But Morley acknowledged he's still hoping for a bit of an evolution for Bellamy's relationship with Octavia, especially in the aftermath of her killing Pike (Michael Beach). "It's a bit of a blow for him," Morley said. "At some point you do have to take a backseat with the people you care about – you can't give them the answer, they have to find it themselves. It's one of those journeys that will take some time. Lots of healing and water under the bridge. It takes its toll."

Working a little bit better? Murphy and Bellamy, who find themselves in a place of relative peace at the start of the year. "At the beginning of Season 4 the dynamic between the two of them is probably the best it's been since the beginning of the show," Harmon said. "Maybe not that they like each other, but I think a little bit of respect definitely has blossomed between the two of them. As a character on the show I think you have to respect any of the other characters that are still alive because you know they've been through something. They're still breathing and I think as a character you just have to give them that respect. Me and Bellamy came back together, saw each other, had to work together and just went like, 'Hey man, good for you, still breathing. That's pretty cool.'"

The 100, Wednesdays, 9/8c The CW