[@shylarah]
I'm fine with the picky questions; they can turn out to be big concerns for a lot more people than expected! 

As a rule of thumb and TL;DR, a character will maintain their normal level of perception, and physical, technological items will work on people that haven't reached that stage of development yet (just don't expect any hyper-rare or synthetic materials to lie around for you to reload your crystal-focused disintegrator with!) 

Now I'll try to target your questions directly (and hopefully expand on my answers so they're not just hyper-specific.) Some further specificity issues may come up, so please ask if there's some other loophole that opens up. 

I'll go in order of asking. 


[hider=Answers]


The guns thing [i]does[/i] fall under "physical tech." You can shoot people, and it will affect them according to their own physiologies. However, if your gun comes from, say, a techmagic setting and uses information from the ether to make sure your bullets will always hit, this property will [i]not[/i] work. If that also means that your bullet doesn't even fly right is something we'll have to discuss. [color=orange][b]If it works from a mechanical and chemical standpoint (relative to our real world) it will work. [/b][/color]

For someone that comes from a technophobic universe, they will [i]not[/i] affect the camera of a person taking their picture. [color=orange][b]The world's baseline physics are identical to our own[/b][/color]. This can be unsettling or a good thing depending on your character, because someone that does not appear in photos will appear in photos taken during the gathering. [color=orange][b]Also as a baseline, people's biologies, unless stated otherwise, are similar to a real human's.[/b][/color]  

The John Carter example may not have been the best one when it came to explaining certain biological feats--as it stands my knowledge of John Carter comes from hazy memories of the movie. If I remember correctly, his abilities [sub]in the movie[/sub] came from being a human from Earth suddenly experiencing less than half of the force of gravity. It stands to reason that if he were some sort of actual superhuman that's a physical ability that he should have retained (although he had the muscle mass of a normal man.) As I don't have a means of measuring the amount of force someone can put out based on their muscle mass, I will have to say that [b][color=orange]physically, to [i]each other,[/i] characters are like mundane humans.[/color][/b] This is a special condition imposed by the Host, and [b][color=orange]if characters agree on it, they can allow others to use the full effects of their abilities on them.[/color][/b] Think of it as enforcing consent between guests [sub]because with a pessimist's outlook, things can get very, very messy if a super-powerful brute viking didn't respect someone else. [/sub]

Unfortunately it would be true that an obligate telepath would feel very cut off from the rest of the characters (save for the above exception), but to that extent the Host has access to a wealth of experience to draw from to create personalities for the servants she will summon throughout the gathering. In the case of a character with a sensory process different from others, their biology is preserved. [b][color=orange]If your character is not human, they will have the same properties as a mundane member of their race.[/color][/b] Further restraints on their abilities are applied accordingly; if they can cleave cattle-like beasts in half normally, they will not be able to do so to other guests without consent. The servants throughout the building are fair game [sub]but please be nice to them. They're there for your sake.[/sub] [b][color=orange]If the species depends on magic to perceive things, they will have access to it to that end, but if they have a special ability like seeing someone's magic capacity, for all intents and purposes, [i]other guests will appear like objects to them[/i] unless they're the same species.[/color][/b]

In the case of examples that you gave me, if your "magic energy" isn't just catching fire, and you're actually superheating air and containing it, that ball of hot gas will definitely hurt people. Please be honest with your character's existing magic though; if they aren't the type to reason that kind of thing out, and their magic isn't explained, they won't manage to get that fireball to do any damage; it'll just fizzle out on contact with another guest. In the case of the spear of ice, it's the same thing. If your magic energy is becoming ice or pulling it from the ether, it'll melt when it touches someone. If your character figures that they can take water and freeze it, it's fair game (which makes ice magic quite a bit more powerful compared to fire magic in this scenario.) The same consent exception remains as above if your character can't figure out manipulating the world around them instead of blindly casting. As for support magics and saving people's lives, [b][color=orange]unless your character specifically refuses to be affected by [i]all[/i] forms of other people's abilities, "positive" effects will have the "positive" effect intended.[/color][/b] The person falling to their doom will stop falling. In the case of healing magic used on an undead character, if the intent is to heal that character, the undead character will still be "healed." If you're trying to be clever and try to harm that undead character with positive energy, the effect will fizzle out. [b][color=orange]Intent is very, very important in the gathering's pocket dimension.[/color][/b] You're in the Host's dimension, so there is no hiding your intentions from the world even if you can fool Gods. Please reason things out in IC and OOC. 

If people want to eat the food that the mage chef makes, that food will be real to them. If they want to use that ice ramp, sure they can. [b][color=orange]As a caveat to the consent rule, if your mage makes that ice ramp and doesn't want other people to use it, they still can. In general, you can [i]allow[/i] people to do things to/with you, but you cannot necessarily [i]disallow[/i] certain things.[/color][/b] You can disallow them from hurting you, but if you make a cake and someone wants to eat it, it will be considered a physical object [i]unless it's poisoned or intended to do harm,[/i] in which case it will [i]not[/i] be a real object to them unless they gave their consent for all abilities. 

Here's a summary and extended listing of some of the rules I just sussed out:

[b][color=orange]
Intent is the single greatest decider in the world beyond the base rules I set out. 
[color=green]Good[/color] intentions will affect people so long as they haven't disallowed all other guests' abilities from affecting them.
[color=red]Harmful[/color] intentions will not affect people unless they specifically allow yours or everyone's abilities to affect them.
[color=pink]Mundane[/color] spells and objects will not affect others unless they want them to.  
The world's dimension's physics are the same as the real world's. For simplicity's sake, we won't take into account if your gun's innards were designed with .78 G in mind, but anything greater than that difference and we might need to have a talk.  
You maintain the biology of the most mundane member of your species, and magic that supports your existence will work.[/color][/b]

[/hider]

[b][color=orange]Please remember that the point of the RP isn't combat, though it's allowed.[/color][/b] I want your character's wounds to be emotional. 

I'll stick this stuff in the main post once I'm not sitting in a car fighting its suspension to type without looking like I've had a stroke. 

Please, bring more questions if you have them.

EDIT: For a grammar error. Also, the Host won't put you in any peril! At least, not at first.
EDIT x2: More grammar.