Sounds like Changeling: The Lost, with some Promethean re: the distrust.

I like chinkeeyong's suggestions. To expand on the "Very careful and specific" part, I can see a person placing a lot of import on words in general. Casual phrases or promises are treated much more seriously than the human speaker intended. "See you soon" or "May you have a good morning" are treated like promises or blessings.

Maybe unusual reactions to things, like flinching at bells because they're used to being around fey creatures who are harmed and outraged by the ringing of bells, valuing certain flowers as much as gold coins or jewels, disliking the taste of salt, being more suspicious of flora and fauna like a robin or an ash tree may be listening, feeling free to partake in gifts left out for fey like just walking up and sipping from a bowl of milk left on a doorstep.

Yeah, it has a little tint of Promethean, although it's generally in a way that you get accustomed to the person, instead of the person slowly breaking down more and more.
I could theoretically play him with some whimsy, but I'd rather play him more like a secluded child.

The way I see it, is that he grew up in faeries. He had a prolonged rebellious stage, and acted like a brat most of the time. Eventually, he got kicked out of Arcadia, as his story ended, and got plunged into the real world. At that time, he found himself in an alien land, and realized how wonderful Arcadia truly was. So he finds himself unable to associate with other humans, and wanders around the forests, hoping to get lost in Arcadia once again. Which, as a magi, he probably accomplishes every now and then, so he needs further goals that that.

I like the idea of overanalyzing general phrases, as he has some trouble understanding intent, and lived in a world of bounding words.

I'll also have to figure out what story he grew up as part of, since it could have severe ramifications on his character traits. He will probably adopt some traits from the Strong Faerie Blood he is related to. I intend to go through Changeling: the Lost for some inspiration, but haven't had the time yet.

Aesthetically, I want him to have this "frost" theme. I'm envisioning a little boy walking around in summer with a woolen robe, mittens and a massive scarf. If you shake his hand, it's probably ice cold. However, there aren't a lot of fitting myths that relate to ice, although I do have some workarounds. And given that I will probably have to make up the tale, I do have some creative freedom to work with.

It sounds like you already have a good idea of your character.

+1 !

I never noticed how huge the Ghosts of Dragonspear Castle adventure was.

Define huge?

Well, I do. But I'm prone to regret, so I figured I'd try to avoid any alluring options before the game starts. Could also serve as some inspiration, since he's not entirely finished yet.

extremely large; enormous.

Went to the Paizo panel at DragonCon. They have some fun projects coming out in the next year that looks pretty fun. I think my favorite thing they mentioned was that they were finally redesigning the Rage ability to not be as number-crunch heavy in a book that will have a lot of redesigns for DMs to use if they want. It's going to be very "pick and choose" for the DM to implement any or all of the proposed changes for their games. Apparently the Summoner is going through a heavy redesign for that book which will nerf it significantly. They also discussed another book that I think they said will be up for public testing soon which was a new set of classes based on an Occult theme. Don't recall too much about it, but there was one class that sounded pretty cool where they are meant to carry nonmagical items of historical importance, and they can imbue them with magical properties for combat and utility themselves.

~SE++

Story of my life.

So you know how 3.5/Pathfinder had the OGL so anyone pretty much has access to the rules for free. Does anyone know any decent RPG systems that do anything like that? I've been in the mood to run something different for a while now but feel kinda limited by the knowledge that few systems outside of D&D really allow you to play unless everyone has a hard copy of the rules on hand.

So yeah if anyone knows any freely distributed rule systems feel free to shout about it. I'm dying to run/play something that isn't High Fantasy right now.

Oh and anything but D20 Modern. I really dislike that system. A lot of little things about it rub me wrong.

You could always try one from here.

~SE++

Might have to look at all of the games on the list sometime...

In other news Gary has found safety from zombies in vault 108... From other things, not so much.

Well, on the plus side, maybe he'll find a Pipboy.

~SE++

Fate is free.
I don't know how good Nemesis is, but I know that I really like the One-Roll Engine.
Everyone is John is sort of fun for one-shots.
Honorable mention to Lasters and Feelings, !Los Magos Del Tiempo! and Car Lesbians.

Apocalypse World is a narrativist system set in a post-apocalyptic world. The full rulebook costs money, but the reference sheets are comprehensive and not difficult to understand (all rolls are 2d6, "hold 3" means you get 3 of a resource to spend for your move, "+1 forward" means you get +1 on your next roll). If you like Pokémon World's resolution system, you should check Apocalypse World out. Note that the tone is better suited for mature players.

Dungeon World is Apocalypse World retrofitted for a fantasy dungeon crawl. The rules are freely available here.

I want to make a power fantasy systems about modern day teenagers being manipulated by adults into fighting the manifestation of people's desires by using superpowers fueled by their own depravity and sadness.

I think you could hack Don't Rest Your Head for that.

I know GURPS has http://www.sjgames.com/gurps/lite/