For this to succeed, it has to reach Hostile status and remain that way, as in it is unrecoverable. To satisfy that, you must actually harm the citizens in an irreversible way (read: kill them, Embrace them, make them your meal). While the pillars themselves are influenced by your choices within the story, the side characters are actually modified by their Blood Quality and the uncovered hints. By choosing to eat them, you will gain the revealed experience when you use your Sense (pressing L3). Embracing enough of them, perhaps around five to seven, will imbalance the entire district, if not completely degenerate it near it. To find out, go to a hideout and rest. Those who aren't Lost or Missing will wind up dead and the district will be overrun with creatures (and Priwen).
I would suggest against going for this trophy without first making a back-up save, as described in the Embrace Clay trophy:
The Hidden Trophy trophy in Vampyr worth 24 pointsContinue playing to unlock this hidden trophy