@mammon hard to say without context (I hate that we don't know why they can't attack) but I'm guessing they either need to stop it without destroying it or they need to do it under certain conditions.
I honestly have no idea how do evaluate the assets of the Evangelist faction. Do they not pretty much have the entire government under their control in addition to having access to demons (or whatever) from Adolla? I mean, here we see a gigantic pillar being raised and a big demon appearing. If they can just pull stuff like that, shouldn't they be able to easily crush their opponents? There's probably a ritualistic reason to why they can't just do that or they even need certain people to stay alive, but it really just feels like a plan to success with detours.
@Muriuki, @AngleBoi7 They really used the giant infernal from the first opening. It may be planned, or the author just liked the design of it, then he decided to use it at some point.