They (the lil microbes inside the chassis) are pretty much the oldest known thing in our universe. The star they live around was there at the infancy of the universe, they found a way to extract and replenish it's core. These microbes are survivors and evolvers...they are also a battery...think Baghdad batteries. They are like acid...ok I don't want to get sciencey....anyways, some of the first beings in the universe survived. They adapted, they freaking cool, and we should really learn that refueling star trick. Edit: oh and there is a reason they want to be known as symbiotic or harmonious, those lil guys power armor and explore the universe through their vessels, their thought ships...thinking flesh...like you.

I (like you) haven't been bothered to read the lore books, and this could very well be (and is most likely) false, but I thought it was cool and wanted to share it. In S11, in the Tree of Probabilities strike on Mercury, when you exited the Infinite Forest, before the sparrow ramp, you could easily see the a Pyramid in the sky. However, the text that popped up in the bottom left said that it was a [i]simulation[/i], not what was actually happening IRL. This means the Vex are able to simulate the Darkness. However, in an adventure on Nessus, (I forget the exact name) there was a line by Ghost as you were hopping around floating Vex platforms above the Tangle. Ghost is essentially accepted by the network, because Failsafe is trying to hack them, but Ghost tells you that the Vex call you [i]that which they cannot simulate[/i]. This means either A. They cannot simulate due to the fact that you are an unpredictable variable, or B. They cannot simulate your light, or C. A combination of both factors. I like to think that it is C, and if the Vex can simulate the Darkness/Pyramids and not the Light/Traveller, this raises the question of: How can the Vex simulate the Darkness and not the Light? I think the answer is simple at this point, the Vex were created by the Pyramids and the Darkness within, thus allowing them to know and be able to predict their creators. But wait, there's more. When Shadowkeep released, the cut scene at the beginning to S8 showed the creation of the Vex inside of something that could easily be a Pyramid, and then walking into the GoS. Now, one could easily say that this was a Vex construct, programmed to create more Vex. But then we also have the cut scene from the end of the Shadowkeep campaign: when you enter the Pyramid and land in the Vex domain. That isn't a coincidence.

The origin of the Vex is implied in the Unveiling Lorebook, chapter 9: Patternfall. The first thing to note is that the Vex are not the machines, but the 'Milk' inside them. That 'milk' is Radiolaria, millions of microscopic organisms swarming together in a saline solution. These organisms are claimed to predate the actual existence of the universe as we know it, and they learned to construct these machines out of silica. As for where the Vex came from, that has to do with the Flower Game, played between the Gardener and the Winnower. The rules of the Flower Game have to do with squares on a grid, which can either be filled in or blank, changing their state based on a set of rules. Within this set of rules, it is possible for certain patterns to keep repeating, and it's possible for certain patterns to produce figures. According to Patternfall, some of those patterns actually escaped the primordial garden where the Flower Game was played, tumbling through the chaos until they landed in saline waters. That is the origin of the Vex.

Rumor has it that an ancient race known only as the Protheans created the Vex, then mysteriously vanished almost 50,000 years ago.

Theyre not machine. Theyre the fluid that inhabit the machines.