'The 100' season 4 air date, spoilers: Unexpected enemy poses the greatest threat

"The 100" is gearing up for its fourth season with the promise of a potentially climactic turn of events happening in its midseason finale. Now that the post-apocalyptic earth itself poses the greatest threat, not even the series regulars will be safe from its wrath.

When the previous season ended, series protagonist Clarke Griffin (Eliza Taylor) managed to destroy the artificial intelligence that brought on the nuclear apocalypse 97 years ago. But they had not anticipated the deteriorating nuclear reactors to gradually irradiate Earth and once again threaten to render it unfit for human inhabitants.

There are speculations that a war may just break out as survival instincts kick in and it becomes a matter of which faction should survive or not. After the devastating deaths of major characters in season 3, there is no telling who will survive and who will bite the dystopian dust in the upcoming season.

Executive producer Aaron Ginsburg and costume designer Allisa Swanson hinted at brutality and possible death on their official Twitter accounts. Swanson teased her fans by musing who might get "maimed, wounded or killed" in a particular episode, while Ginsburg shared how he was working on the "most twisted brutal episode" of the series yet.

The hinted episode could also be referring to that particular point in the upcoming season when a blanket of thick, dark, radioactive-charged clouds rushes towards Polis City as shown in the sizzle trailer for season 4 presented during the San Diego Comic-Con 2016.

Series creator Jason Rothenberg said during the event that season 4 will not be about stopping an unstoppable enemy. Instead, it will deal with the question of what would these people do in order to survive?

"There aren't enough lifeboats," Rothenberg added, "so who gets to choose who lives?"

Some characters will also be coming on their own with Octavia Blake (Marie Avgeropoulos) taking a dark turn and Clarke regaining a position of authority with far more confidence in herself and respect from her elders. Raven Reyes (Lindsey Morgan) will also be undergoing an evolution following her close encounter with the artificial intelligence ALIE and may just become strong and wise enough to take on season 4's big bad.

Just as new characters are expected to be introduced in season 4, old ones will also be making a comeback like the King of the Ice Nation Roan (Zach McGowan) and the Chief of Tondc Indra (Adina Porter) who has survived her mortal wounds in the previous season.

Filming for "The 100" is still ongoing and The CW has yet to announce an official release date for the fourth season. It is, however, expected to air sometime next year.