The Vex have existed for billions of years & were on earth before we ever were. The Vex Data Milk actually contains radiolarians (protozoa found as early as the Paleolithic era). The Vex were born in the Black Garden, as are the ghosts, but they weren't always the way they are now. Their original purpose was to tend to the garden, but it was the arrival of the Black Heart that changed that. The Black Heart was created by Lupi (the Traveler) unintentionally. All of this is supported by these grim cards: Ghost Fragment Traveler Ghost Fragment Traveler 2 Legend: The Black Garden A Stranger's Call Undying Mind Hobgoblin Ghost Fragment Vex 3 Sol Progeny