So here is what I believe the sides will be for the start of the final battle in Lightfall. Traveller/Light side: Guardians, humans, awoken, most exos (some may be turned against us, they do require the Alkahest which contains “Clarity” after all) Fallen House of Light as well as the Spider and his people. Cabal faction led by Caitl and possibly Calus if he still lives and is not corrupted. Very slim chance but if we start winning it’s possible a group of Vex will calculate our odds of winning and decide to join us but only to be on the winning side (similar to how the Sol Divisive calculated that they couldn’t beat the Darkness and worship it). This is unlikely though and will only happen late in the battle. The Nine (not sure if they will be there in person but I think they may help in some cryptic way we won’t understand). Darkness side: The Hive (I don’t see any of them turning). The Taken (whoever will be controlling them at that point, not sure if Quria or Savathun will live beyond Witch Queen) The worm gods Whatever Cabal faction betrays Caitl or has gotten corrupted. Miscellaneous Fallen and Fallen houses that join the darkness out of fear and the remnants of House Salvation. Sol Divisive Vex and any other Vex that start to see the Darkness winning in most possible futures. Corrupted guardians (not every guardian that has wielded the darkness but those who let it control them). Possibly some corrupted exos. A potential new enemy that is closer to darkness incarnate (like the Veil theories if they turn out to be true). PS to clarify I’m not thinking all of these will be involved in actual gameplay combat or even cutscenes. Some we may only hear about through lore.