The Lore behind The Vault of Glass

Beneath Venus the Vex have constructed a massive structure that is acting as a meeting point of past, present and future. Their long-term goal is to basically unchain themselves from the constraints of a physical reality and turn themselves into a sort of epistomological computer virus in the very fabric of reality, incorporating the very IDEA of themselves into the fundamental laws of the universe. Because in this space, reality and time are starting to be altered, Oracles and Gorgons are basically quantum supercomputers that calculate reality and utilize a weaponized ontology to determine what is and is not real. This is why a Gorgon can look at you and kill you, because it simply unwrites you from existence. Oracles make changes and revisions to reality, and the Templar/Aetheon processes these calculations into existence. The relic is the last, dying, desperate act of Kabr, a guardian who managed to send word that this was happening. He basically killed a Gorgon himself and hammered its corpse into a vessel for the Light, turning it into a shield that maintains a small space of stable reality around it. Throughout the raid, the Vex are constantly trying to separate you from it, throwing it into the past or future where it can't be used against them. All the guns and armor you find in the raid are the remnants of Kabr's failed raid and will give further info about their wielders and the events of the raid itself. In fact, some of the general exotics in the game once belonged to friends of Kabr too. The Super Good Advice machine gun is one such example but comes from the exotic bounties. This was crafted by a hunter named Pahanin who passed Kabr's warning about the Vault from Venus. After witnessing what happened to Kabr he became deathly afraid of being alone; he reckoned that he could only continue existing as long as someone was able to perceive him. So, to ensure that a mind could perceive him at all times he used an AI gun. (Reddit.com)