I am halfway trough so i dunno.
Alright. Have you done the subway? I'm just perplexed how Alan write all that shit, to be able to escape the tunnels.
Yeah, what i think is basically otto guy said:
The "real" alan is the one in the writing cabin but he can project himself in the dark world as writing. This is like basically astral projection. In the dark world, the effect of his writing are almost immediate (aka how the angel lamp mechanic and story board work). He has control of reality there as long as the flow of the story makes sense. The echoes are probably past stuff he has written both in the dark room or real life, so he can change these scenario as a whim.
This is how the game mechanic work. As for why alan have to write to escape is because he cannot escape from the cabin room. In the dark world, there are probably doors, or other beings that has access to the multiverse like ahti or even jesse from oceanview motel that is a nexus of many different plane of existence. since alan cannot access these breach(es) himself, he exploited the same mechanism the dark world use to manipulate the real the world, aka writing. Other than that, the actual mechanism is vague on purpose.
For context i think, control is very important piece of puzzle at least to know what is the scope of alan wake's scenario. Basically the world has different level and plane of existence. The dark presence is basically the darkness version of the hiss. These are just extradimensional beings that lives in other dimension. The darkness is just one of many. Some of these beings are either benevolent (like polaris from control), neutral like the board that have their own agenda but not outright malicious like the hiss or the dark presence.
Now where these planes of existence brush off with part of material world they usually causes supernatural phenomena. Sometiems it affects objects or a small range of spaces sometimes it's big and can cause disaster level of destruction (like bright falls or ordinary from control) alan wake's story is just basically one of this.
The quirk of the dark dimension is if is in contact of the real world, it can absorb fiction and affect reality. This is separated in 2 levels: how if affect "reality" in the dark world and the real world.
In the dark world the effect is immediate and strong (think it as a very malleable world like limbo from dnd).
In the real world rhe effect is subtle. You can't say x will happen and it will happen. You say x happen, it just kinda nudge causality (but this is still very vague). I dont believe the power is that strong and i do not agree alan wake/the darkness caused control to happen or FBC to exist. Assuming the board/the dark presence/the hiss has almost equal level of strength i doubt cauldron lake can make other eldritch beings exists.
Another common thread is these beings have "chosen" one to say basically human agents to exercise their control in the real world. They nudge people towards the breach of dimension and attract people compatible with their powers. For examlle bright falls tend to attract artists (like tammy who you speak early in the game and other people from journals you find)
So basically the dark presence trapped thomas zane, but he got out from writing his way out, then alan came, he got trappec so he must his way out.
