Not sure what you mean?
We have pretty much every monster in Doom series already. My idea merely bridges the gap by saying humans in our realm would be able to occasionally glimpse the other realm and see how messed up it is compared to ours. Those people would then fill in the gaps and created a religion based upon each glimpse.
Religious tomes are already in game. Heck the devs could even have a few places where NPC’s talk about this using just what I wrote describing it…minus the Doom reference of course lol
Survivalist Diary:
Those things man! I swear its like…something out of(fill it the religion flavor of hell).
Scientist Computer Log:
When we broke down the barriers from our world to “Theirs”, we could not have expected how different…and how dangerous it would be.
A great example would be the film The Mist(2007). Assuming the Doom idea was not to every ones liking. The mist describes a story similar to how the demons and gates work rather nicely. Not being able to breathe though…not an unrealistic idea, but instantly dying walking through would be rather bad. I mean think of it this way, play the game without any for knowledge as you would be a normal person coming upon a gate. As a player you would die once and know the next time. But it would be unrealistic, because we have to assuming you would be like “HMmmm…try walking through it…sure, why not?” dead!
So it it would make a lot of sense to have an atmosphere similar to what a human could survive, seeing as monsters can already enter the human realm. Can you stay alive for long? Sure maybe. But could it be poisonous and slowly kill you? Would make for better game play. Forcing everyone to fight in a certain area to cleanse a rush of monsters from a gate you would drop dead instantly…well…seems a rather bad idea.
I’m thinking about it. If I"m a janitor, why would I know how to use a power suit. Even if I came upon a gate, would this person really think…tons of monster pouring out…check! Rambo mode initiated, check! Spear made out of a broom stick and a butchers knife held with duct tape, check! Hold my breathe, pucker my sphintor, I’m going in baby!!! YEAH!!! Dead… >_>