Main post on Coloratura.
I approached the question of souls, dimensions, and auras as though from a blank slate, looking to create potentially interesting and new ways to present otherworldy concepts. I wanted to first create a consistent foundation for Coloratura's mythology, and then to draw puzzles and implications from that foundation.
The very first thing I had decided upon was the notion that souls permeate a creature’s entire body. This naturally led itself to the puzzle of the meat monster, which was a concept that I was enamored with very early on. This also helped create one of my favorite details during the joining with the Engineer: when the creature realizes that it doesn't have to pull each limb, but only pull on the neurons.
This matched soul-body approach meant that anything a human touched would rub off some of the human's aura onto the object they had touched. I described objects as though they were stained with that human's colors at that moment of contact. This was most apparent in the dirty laundry, I think. This gave me an opportunity to color rooms and objects with some understanding and ambient auditory information. I didn't explain this color rubbed-off phenomena all that thoroughly, because I felt it would get too heavy when really it was intended to just explain away why the Aqueosity could kind of understand what human things were about.
The pan-dimensional aspect of living creatures was another interesting aspect to tackle. I visualized this using more accessible dimensions with X and Y coordinates, and imagined each creature as a rectangle with a fixed area, but with changeable lengths.
The length representing the physical, and the width representing the metaphysical. A creature could have a larger presence in the physical, but they would lose their grip on the metaphysical. The Aqueosity was able to manipulate its own footprint (and others') within the metaphysical, but because awake humans were so one-dimensional, there was just absolutely nothing for the creature to manipulate. This allowed me to offer the player the very real attempts to murder the crew that ultimately couldn't implement. I've illustrated how I visualized several of the various sentients in different situations.
One of the things that I felt was important when making up this mythology was to avoid an “anything goes” reality. In the concept phase, the detail of the astronauts who “saw” the alien started off as a subplot where the Captain's mother had been ostracized for going crazy on the moon, and the Captain saw this creature as first a guilty reminder that she had shunned her mother as well, and then as a shot at redemption if it were captured. It would ultimately have been revealed that there were no moon aliens at all, pouring more salt into that freshly opened wound. I downgraded this thread a lot to focus more on the main plot of the game, but the detail of the non-existent moon aliens managed to stick around as a small Easter Egg for those who read the Captain's notes after she vacates her room.
While I wanted the game to be make some sense, I didn't necessarily want the full workings of the mythology to be bared: I wanted to keep some mystery to the process. Even though this ancient Aqueosity is very intelligent, it only cares really about practical applications, the same way that a pitcher doesn't necessarily do or understand physics calculations. The protagonist just acts with a reasonable understanding of the world and the potential outcomes. On the whole, I think my new approach to pan-dimensional interactions successfully gave the game an off-kilter and unique world setting from which to draw from. It really came together to help set the unbalanced, creepy tone of the game.