I like that guide a lot. I've been working on making something of a FAQ for a bit, and I thought it would make a good companion piece to your field guide (this FAQ is meant for people up to date on the comic, but perhaps still confused on certain issues). Zack ends up repeating himself a lot answering the same questions in the comments, so I tried to pull together his answers to the more common ones:
1) Will there be a book? What about other merchandise?
A: Zack pretty much always says something like "definitely, but later" to both questions. Get more friends reading, and it will probably happen sooner!
2) Is the ending planned out / how much is written / how long will this go for?
A: Zack has definitely confirmed a planned end date, though we are nowhere near it yet. He has the entire plot planned out, but not specific things like dialog yet.
3) Is _______ inspired by or an homage to (some other comic/manga/game/show)?
A: No it is not. And stop asking lol.
4) What IS a spectral really?
A: A human who can see and interact with the spirit/ghost world, caused by long-term exposure to supernatural phenomenon, a near-death experience, or possibly other methods not currently revealed. Zack frequently describes them as having living and ghost attributes together in one body, thus they can interact with both worlds. Their development is first marked by seeing faint, wispy purple images of spirits and ghosts called shades.
5) What is the difference between a spirit and ghost?
A: A ghost is what you think it is, left behind by a dead person, and resembling them. They eventually get all "white and forgetty" then pass on. A spirit is a more exotic entity that was never of the living world, and can be significantly more powerful.
6) Why do some spirits/ghosts pass through walls and physical objects but others seem to treat the real world as solid?
A: Some (like Lefty) are poltergeists and can easily manipulate the physical world, or phase through it if they desire. Others (like PJ) just interact with the world as if it was real (such as appearing to lean against counters), but it actually isn't solid to them. However, no ghosts or spirits can phase through active spectrals, who are just as solid as other ghosts/spirits to them.
7) What are tools and mediums? How do they work?
A: A tool happens when a seriously wounded spirit possesses an object, rather than fade away into non-existence. A spectral is lured to it, and gets to wield the spirit's power through the tool. The spectral emits energy which replenishes the spirit, until the spirit eventually emerges renewed, and the tool becomes normal again. If a spirit possesses a human, they in essence become the tool (called a medium), and use the spirit's powers directly.
) Can someone have two tools / Can someone be a medium and have a tool?
A: Yes, and yes. But the spirits might not get along, and they would have to share energy, so not usually.
9) Can a defeated spirit possess a normal human?
A: Yes. The human will be slowly turned into a spectral by this. But possessing an existing spectral offers a quicker recovery for spirits. Prolonged exposure to a tool could also turn a normal human into a spectral.
10) Can spectrals use tools of different color energy?
A: No. Although, non-spectrals turned in to spectrals take on the color of what caused it.
11) Can normal humans see _____ ?
A: Variations of this get asked a lot. Normal humans cannot see or hear spirits, ghosts, or spectral energy. However, Zack has confirmed that normal people see things, even normally impossible results, that happen because of spectral/spirit/ghost/tool activity, like Ed's missing face and Isaac's glowing eyes while in a trance. Ed's paint is unusual in that it appears to be a purely spirit-based substance and thus is invisible to regular people. Almost everything else is visible to normals, like Isabel's paper, Isaac's lightning, etc.
12) What is the Sphinx's power?
A: Sets up a game such that if the conditions are met, reality alters to make something happen. The rules have to be specific and agreed upon at start (though participation can be considered tacit agreement).
13) How does the spirit trance work? Is it "real"?
A: A newer question following recent reveals. Stuff in the background is not real to other people (cannot be perceived or interacted with, not even by other spectrals), but it is very real
to the one in the trance. They can walk through a hole in the wall that no one else sees, climb junk that is not real to their friends, fall to their death as a result, etc. Combine that with the drastic slowing of time to the spectral, and Zack has noted that significant possibilities result.
14) What is (question that inadvertently reveals a future spoiler)?
A: WHO KNOOOWS?
Hope you liked that, please everyone feel free to add on additional answers, or suggest changes to existing ones. I see this as a work in progress, and would like the community's feedback.