Jayla, dead, her eyes are gone
Sadie, dead, body  ripped apart
Jisoo, dead, voice taken away
Sunny, dead, one eye got taken
Michael, dead
Alexei, dead
Nathan, dead
Nelly, alive
Jasmine, alive, spreads rumors about other coterie members ( Sunny, Michael,.. )
Kayden, alive
Nicholas, dead, heart taken   away

The coterie is like ,, Lana's friend group "

Also coterie means:,, A small group of people with shared interests or tastes, especially one that is exclusive of other people.
"a coterie of friends and advisers".
But Lana starts acting weird. That is because Lana was captured. The doppelgänger was pretending to be Lana.
Fake Lana started to sacrifice the coterie members, one by one ( expect Kayden and jasmine ).
She needs their body parts for Agamemnon, to get him to immortality.

The coterie did fight against Agamemnon at first but then Lana got captured by Lina, Agamemnon, the doppelgänger,... and her doppelgänger started to pretend to be her and people believed it.

So, the coterie is basically a group that gets  sacrificed.