@Durin, how to geller fields work in Embers? In canon they worked by creating a bubble of reality, making it so that anything inside was subject to the same rules as the Materium's. (So daemons could only enter a ship if they were summoned, but psykers could still use powers just like they could in the Materium.) Geller fields worked in the Materium too, but were entirely redundant and effectively did nothing unless the area was particularly warpy, but psykers could still use powers and daemons could still enter if summoned (or if they had some other way to get into reality, such as the daemons that invade Avernus seem to have).