Space zombies? (This is very similar to yours) Fallen? Ok, the fallen are only similar to hive thralls. So I think wizards or high powered hive leaders resurrect the dead dregs and vandals into hive thralls and the rest of the hive is it's own race, now let me go more into this. Why? I think this the rest of the hive behavior is smarter and they get behind cover. But the thralls go in and attack like what I have seen from the fallen the most. And the acolytes and wizards look very different from most of the fallen and hive thralls. I bet your saying "Pro this makes only 5% sense" well hive wizards are dark, evil u could say, and makes most sense if they use black magic. In the list of spells that are considered "black magic" is resurrection. Do u see it yet? No, well let's move on to why I think the hive are there own race. I have 2 theories for the hive so let's get in to it. The hive could be mutated fallen guardians wizards=warlocks but this very doubtful. On to the more likely theory, the hive are a wiped out civilization that has been mutated and brung back by something, the traveler…, and they now work for that thing and has to do it's biding. Why I think it might be the traveler. The traveler might be a living being. Since the the city is waiting for it to wake up and the traveler is simply tricking us by bringing on the golden age. The traveler is the darkness controlling the hive, cabal, and fallen. And the vex came to stop us cause they know we will stop the traveler so they went back in time to try and stop us cause they think the traveler is good like we do. So the vex is created by what ever lives in the future. Now back on to the connection between the fallen and hive. One last piece of evidence, the hive have big green eyes, but yet the thrall don't. The fallen when they die maybe their eyes decay fast along with their ears or hair depending if they are a dreg or fallen