Clarke Griffin (Eliza Taylor) is considered the “key” to the last war humanity will fight in the final season of The 100, but what exactly that means hasn’t been revealed yet. While there is a war brewing on Sanctum — where season 6 was set — that’s not where all of season 7's plot setup occurred. In fact, Clarke's importance to humanity, and the impending war, are rooted in events from the show's early seasons.

The buildup to humanity’s last war is happening on Bardo, another planet connected to Sanctum and Earth by the Anomaly. Anders (Neal McDonough), the leader of the Disciples on Bardo, talks quite a bit about humanity’s last war, which he believes they’re about to be involved in. Since the arrival of Octavia (Marie Avgeropoulos), Anders has been convinced that Clarke is the key to this war — the only question is why.

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While The 100 is holding back a lot of details for the season, there are enough hints in previous seasons to get a pretty good idea of why. The reference to Clark being a "key" is telling: the most prominent use of the word “key” in the show was in season 3, when the chip that brought people into the City of Light was called “the key.” Furthermore, Clarke surviving the City of Light was specifically referenced when going through Octavia’s memories, so while both using the term “key” might be a coincidence, there’s likely a connection between the two.

The 100 Clarke ai A.L.I.E. season 3

Clarke has a strong connection to A.L.I.E., the artificial intelligence created before the first nuclear apocalypse by Becca Franco (Erica Cerra). In the season 3 finale, Clarke took the chip to enter the City of Light, making her part of A.L.I.E., but her connection didn’t end there. She also took the Flame, a more advanced version of the AI that the Grounders associated with the Commanders. She also still has the Mind Drive that once held Josephine Prime’s personality, also technology developed by Becca.

There’s a strong religious element to the City of Light that would connect it to the Disciples. Not only is the name evocative, but it served as a digital afterlife for anyone who died while the chip was implanted. Clarke still has the key to the City of Light in her head, as it helped her survive getting her mind wiped. This would imply that the Disciples want that chip to help recreate the City of Light, and Clarke is the key in that she’s how they’ll create a perfect world without war.

Anders could also be mistaken about Clarke’s role in the upcoming war. They never finished scanning Octavia’s memories, which would include events like the destruction of the Flame. If the key is the more advanced version of A.L.I.E. or something similar, then the Disciples are going to be disappointed in how their war goes. Regardless, The 100 is setting up Clarke as central to humanity’s last war. The answer lies in previous seasons: she has a unique connection with some incredible artificial intelligence, which could be the key to winning the conflict.

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