Calyx could be, or have relations to, Demeter/Halmarut.
This is just an evidence dump based on this Reddit thread with some extra stuff added. Feel free to chime in with any corrections, thoughts, or evidence in either direction.
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β Halmarut was an Ascian specializing in plant life.
"Calyx" refers to the outer green part of a flower (plant life).
Following the Ascian/Greek naming convention, Halmarut could've been named Demeter, because Demeter was the goddess of "harvest" and "agriculture" (plants).
Calyx, Halmarut, and Demeter all share a plant-based connection.
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β‘ We were shown that Director Demetrius was very devoted to Calyx. Killing Preservation members the moment they express doubt in his vision...
...and having a locker full of pictures of Calyx.
His name literally means "dedicated to Demeter." This name would make perfect sense if Calyx was actually Demeter--since he clearly ain't dedicated to anyone else--and would give a reason as to why SE went so over-the-top with depicting his infatuation (wanting us to draw the connection).
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β’ Calyx creates his own version of Necron, which uses some argicultural attack names:
Soul Reaping
Crop Rotation
And seasonal attack names (see β£ below for more on why these are relevant):
Cold Grip
Seasons of Blight
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β£ Calyx referrers to his "Winterer peers" to the Ascian (?) in the final cutscene of 7.3.
Since he calls them his peers, it's implied he's apart of this organization, tying him in a literal sense to the season of Winter.
In Greek mythology, Demeter is mostly tied to Winter, too, since the story of her grief brings upon the season and is supposed to be the explanation as to why we have seasons at all.
This could also be why he has such a "cold" nature, and why his overall appearance--from his hair to his eyes to his skin to his clothes--is so pale and "cool," which thematically could evoke the chill of Winter.
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β€ Calyx calls what he's doing his "harvest."
WoL even has the choice to repeat this very specific phrase.
Reminder: Demeter is the goddess of--specifically--harvest.
