After obtaining their base, the spirits must have stopped controlling the apes which resulted in random raids that are too well known by the inhabitants of Port Hope and that formed their opinion about those creatures. The lack of organisation and control in those attacks makes it obvious that there is no higher power behind them. It seems that the spirits have now left the pyramids since the rare reports we receive from that place, tell us that the once grand structures are now overgrown ruins. Would the spirits allow their home to decay in such a way? I would highly doubt that. There are only two explanations for this phenomenon. The first possibility is that the spirits have left our world. This would be reasonable if you assume that taking control over a living being costs some powers and might have drained all energy from the spirits. But wouldn't those pyramids cancel this effect? For sure they would. So another reason for the spirits' departure could be that the spirits gathered enough energy through the pyramids that allowed them to travel to another dimension or reach a new state of being . So the spirits have no use of the pyramids anymore. The second theory for the spirits' disappearance is much more worrying: the spirits are only asleep. Perhaps the process of becoming one with the field energy of the pyramids was so exhausting that the spirits had to take some rest. If this is the case, they could wake up anytime. And nobody can foresee how they will react to us living intruders who could pose a dangerous threat to their spiritual home.