Might just be some lore i missed, but doesn't the existence of the disciples confirm that the pyramids aren't piloted by any one race? then again, tormentors.
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Each Pyramid seems to hold one individual disciple of the witness. Nezarec on the moon, Rhulk in Savathun's Throne world, Calus getting his own Pyramid too, the unnamed one from the Europa pyramid. It plays perfectly with how everything light and dark mirror one another. The Traveler lifts entire species to the light The Witness gathers individuals for the dark Going by Rhulk and by Calus, the Witness' disciples also all seem to be individuals who have been trouble or went through some hardships before they were witnessed.