First of all, I just walkthroughed the new mission for me, in which you visit the huge underground city. My regards to your lever-designer, Fatshark. The visuals of this, the art of tech-gothic… Just magnificent.
Yet we don’t really enter any Cathedral on our way. The new mission type for that -
We approach the Cathedral
in which heretics created 2 or 3 altars. Those altars can only be destroyed by melee, and they have some huge amount of hp, so there is a choice - the whole team tries to destroy the altar with their swords to make it as fast, as possible, or only 1 player begins to destroy it, while all the others cover him from hordes, that come to defend the altar.
During Halloween, or some events, or special missions these altars may be changed to daemonhosts with the same goal - cleanse the Cathedral.