If you havent read the books of sorrow ( [url=https://www.bungie.net/en/Forum/Post/153754344/0/0]link[/url] ) here is a summary of what they say The worms are the darkness, ancient enemy of the traveler. This starts on the fundament, where the worms grant the hive eternal life in exchange for "food". After the hive become immortal, the worms motivate them to take to the moons and kill the traveler. They try to kill it, but it flees and bestows a golden age on a different race, until the hive arrive, then it runs away if the race isnt able to defend the traveler. This cycle repeats. Eventually, the traveler reaches the eliksni AKA the fallen(this is based off of HoW grimoire) But for whatever reason, it leaves prior to the fallen being wiped out by the hive ( im not sure if the fallen even come into contact with the hive) this causes the eliksni to follow the traveler to seek revenge on it for abandoning their race. Sometime after the eliksni encounter, the traveler reaches earth, and starts a golden age. Something goes wrong, however, in fact, three things go wrong. Crota and his minions, the vex, and the fallen arrive. Starting with Crota and the Vex; Crota's 2 sisters ir anuk and ir halak were experimenting with wounds (hive portals) in oryx's throne world and they were trying to make themselves harder to kill by dying in this wound. Seeing that oryx was pleased by this, and told how by savathun, oryx's cunning sister, crota cut a wound in the throne world and by doing this, he let the vex in. This was savathun's will, not crota's, keep that in mind. After eradicating the vex from the throne world with his 2 sisters, oryx saw what had transpired and he says, "come back victorious or die forgotten" and proceeds to cast oryx into a vex portal. Crota proceeds to battle through history (we do not know where or when exactly) and becomes a "legendary demon". Through his journeys, he resents oryx for doing this to him, but he understands it with time. Crota begins setting up shrines to his father, respecting him for what he did. Eventually, crota's hive end up in our solar system. The eliksni arrive and land on earth, and begin to prepare an attack on the traveler. The vex have been hunting the traveler, too, this whole time, and they set up on venus kinda when the collapse starts, but also kinda before humanity exists. It's weird. This is where the collapse begins. Crota remembers his fathers motives against the traveler, and tries to help him, he does this by seeding earth with hive. The hive and the eliksni both mount an attack on the traveler, thus crippling it. In the aftermath of this, the fallen attack the city in the battles six fronts and twilight gap. Shortly after this, you come into play, commencing the end of the darkness. Now, the worms are not actually the darkness, but they have the closest connection to it. The darkness is actually the thing they refer to as the deep. From what we know, the deep is not a race, but it is a place/single entity, a kind of anti traveler, bent on tricking things into fighting for it, just as our good traveler does. The difference between them is that the deep does its work by physically influencing races to work for it. The worms are kind of the ghosts of the deep. Our traveler does its work by mentally influencing us to advance ourselves in such a way so that we can protect it. This is why ghosts exist outside of our bodies, and worms exist inside of hosts. At least thats what i think. If you see any flaws, write a polite message in my replies, i will most certainly respond, oh reader mine. Also, special thanks to Tree of Ruin for sharing all the grimoire with the community.