I'm thinking atheon, while not all the facts point to him some do such as stating that this is endless, time is endless and atheon controls time within the vault. Another thing to back this up is when you said many have tried to reach me but failed, this could be hinting to kabr's team getting into the vault, suposingly no one from the team survived. The vault could also be classified as a prison because it is incredibly restricting to the vex and their powers.