Looking further into the Grimoire, The Vex cards offer quite an interesting story. We have the Precursors, the original Vex created long before those we face today, and we also have the Descendants, The Vex of the future. Does their exsistence assume we ultimately fail our goal to free our solar system? Going off the theory that our world is a Vex simulation, then ultimately our fight was worthless the second we were revived. Our fights against the Darkness pre-calculated years in advance, all efforts end up only ending in nothing.
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The lore suggests the vex have definitely succeeded in some realities, and possibly even all realities at the moment, that's what the guardians are trying to fix by destroying the black heart and killing atheon.