The fallen are just out to reclaim the traveler for their own, because it left them. So they don’t really pose that serious of a threat unless you look at the battle of the twilight gap. The cabal are just power hungry seeking to claim territory and destroy planets but don’t really pose enough of a threat either (For example Ghaul and the red legion) even if the almighty destroyed our sun, the traveler I’m pretty sure would live on unless I’m wrong. (You can correct me) The vex are pretty malevolent and are one of the darkest and evil species and are pretty rampant when combined with the taken (Quria) Then we have the Hive and the Taken. Honestly as far as we’ve seen since destiny 1, they have been the main antagonist of the franchise so far that has been the most active fighting against us and the light. We’ve had basically 2 raids for both species (Crotas end, Kings fall which was both hive and taken, and then the last wish which is primarily taken). These species are very clearly the most linked to the darkness as far as we know. But we can’t be sure that they are the ones inhabiting the pyramid ships. Whatever is inhabiting the ships are clearly far more malevolent than the hive and taken. Those ships are the reason the collapse happened and why the golden age ended so I don’t think it could be anything we’ve fought before.