Hiya!
That would be the Dungeon Master. You know, the "unseen and unknowable force of all of everything".
In fact, in my BECMI/BX/DD games (all of them) the whole "Immortal" path thing, where there are the "old ones" outside of even the regular Immortals...has an "outside of even the old ones". That outside is our actual reality with you, the DM, sitting at your table scribbling notes about how "The fetching young laundry maid is actually a 'reformed lich' that uses Shapechange every day".
^_^
Paul L. Ming