The 100 type TV Show network The CW genre Sci-fi

“Is The 100 ever about sunshine, flowers, rainbows, and people getting along? No! Heads will roll; there will be blood.”

Marie Avgeropoulos’ characterization of The CW’s post-apocalyptic drama is a perfectly apt description of the third season in particular.

When the show returns for season 3, viewers will see the characters after a three-month time jump. “You get to see where everyone’s temporarily settled and tried to find their feet,” Bob Morley, who plays Bellamy Blake, says. “You’ll see that a little bit before everything turns to s—.”

War came before, and it’s coming again. That’s no surprise. But the source of that conflict is the big question. Show creator Jason Rothenberg says season 3 has two major story lines: “The grounder conflict — [as in] where do the Sky Crew fit in with the Grounder 12 — and the A.I. story.” EW spoke with Rothenberg, Avgeropoulos (who plays Bellamy’s sister, Octavia), Morley, Christopher Larkin (who plays Monty Green), Eliza Taylor (who plays Clarke Griffin), Devon Bostick (who plays Jasper Jordan), and Richard Harmon (who plays John Murphy) — it’s a big cast! — about which of these two threats we should be worried about going into this new season.

First up is the Grounder conflict. In the season 2 finale, the Sky Crew eliminated Mount Weather, an underground civilization that had been killing the Grounders for decades. So shouldn’t the Grounders be praising the Arkers? That’s not exactly what’s happening. “There’s that underlying threat always between the two of them and both parties have the ability to take power,” Morley adds.

Larkin echoes this sentiment, saying there’s a fine line in the Grounder/Arker relationship. In season 2, the two groups were able to work together because they had a common enemy. “Now that that common enemy is gone, we’re left to deal with that relationship again,” Larkin says. Or put more simply by Bostick: “They’ve gone from enemies to frenemies. [The Grounders] seem like a clear villain at the beginning, [but] we slowly learn that they are just like us.”

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If the Arkers aren’t going to war with their frenemies, whom we know, the source of conflict may be from a new face: Ice Nation. Although we were technically introduced to them in season 2, we know very little. We know they are responsible for the death of Lexa’s first love, we know they live on the outer edges (of the lands we’ve seen so far), and we know they are fierce.

“Out of the 12 Grounder clans, Ice Nation is easily the most terrifying,” Larkin says. “If you’ve been horrified by any of the Grounders before, you haven’t seen anything yet.”

Part of that horror comes from the fact that they’re refusing to take part in Lexa’s coalition of clans anymore; they want to rule themselves, says Taylor. She compares Queen Nia, played by newcomer Brenda Strong, to Clarke in some ways. “They [both] do whatever they have to for their people. I think they can see eye to eye in that way, but Clarke has a good heart and the Ice Queen does not.”

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And that’s when things start getting political — which Harmon says is his favorite part of season 3. “You definitely see the juxtaposition between the Ark politics and Grounder politics,” he says. “Their [politics are] very different … but the end result is seemingly the same.”

And in that way, it could change what we expect from this season’s “war”: “There’s a lot more war with words and rules as opposed to, like, spearing each other,” Taylor says.

But let’s not rule out another character who could be good at a war of words: A.L.I.E., an artificial intelligence who we last saw standing next to a nuclear warhead telling Jaha they have “work to do.” “That’s pretty terrifying,” Larkin says. “I can’t see that ending well.”

And if all that didn’t give you enough to think about, we’ll add this: Rothenberg says the way the Grounder conflict and the A.I. stories connect will be “a big reveal.” So maybe the answer to our original question — Where does the season 3 war come from? — is all of the above?

Either way, there definitely will be blood. Avgeropoulos adds: “People pay for their repercussions on The 100, and it’s just a matter of when it happens and how it happens and what kind of strategy and alliances you have.”

The 100 returns on Thursday, Jan. 21 at 9 p.m. ET on The CW.

—Additional reporting by Natalie Abrams