My answers to Abadd’s little “questionnaire”:
The Ancients who created the Towers must have been at least relatively powerful in the Ancient Age, as they built the most sophisticated technological apparatus (i.e. the Towers themselves). According to some quotes, these Ancients were apparently opposed in their own time by groups who did not want the Towers to be built. This might imply that the Towers’ purpose was malign, which would fit in well with the quote that said the Towers eventually “burned three continents in a night” (and thus my Tower/apocalypse theory above).
We know that the primary Sestren AI operated the Towers, and that the Sestren System itself ceaselessly monitored the world. It could have been monitoring the world so that the AI would be better equipped to heal the environment via the Towers; that would make sense. (At the same time it might have been keeping tabs on how much of a threat humanity was becoming, for similar reasons.)
As I said above, the towers’ original point may have been to wipe their creators’ enemies off the face of the earth (but only those vague quotes really imply this). Their point after that was apparently to purify the world and repair the environmental damage that had happened before (for whatever reason, war or the Towers themselves). The purpose of the pure-types that they produced seemed to be to protect the environment from any and all possible threats. (And possibly to stop humankind from really getting anywhere in the meantime).
They were probably multi-purpose tools originally, but Abadd’s final purpose was to “resusscitate” his masters, who were probably the ones who created the Towers. They evidently wanted personal survival after the planetary healing process was complete, and the fact that they had planned to go into hibernation hints that they were either the ones who caused the worldwide devastation, or that they knew their Towers were going to make the world pretty inhospitable in the meantime.
Whoever built the Towers probably went into hibernation / stasis; whoever didn’t build the Towers presumably got the worse half of the deal and became the current human race, eternally oppressed by the Towers.
The entity that was meant to forcibly turn off the Towers after the planetary healing was completed? It said itself that its purpose was to “return the world to the hands of the people”, so that could mean the slumbering Ancients just as easily as it could mean the current human races.
Possibly: Sestren hadn’t been able to finish its planetary repair job by the allocated time that the Heresy Program was meant to go active. That would explain why it was fiercely opposed to the Heresy Program performing this forceful shut-down. If the planet wasn’t ready for habitation yet, because the Towers had become worn down / were damaged in the past, Sestren might seriously be unhappy with the Heresy Program trying to bring the whole thing to a close. Which it did anyway.
The previous Divine Visitor. Obviously.