I'll take this opportunity to talk about the three kinds of magic, which is necessary to explain exactly what the yellow chibi Kor and the purple chibi Tin Can ARE.
The first kind of magic is called Ecco, which is about as common, useful, and necessary as air. Essentially it is 'The Force' from Star Wars. Everything gives off and absorbs Ecco: trees, animals, rocks, water, stars, everything. Ecco is invisible, and is probably responsible for keeping life, the universe, and everything working in it's normal way. It moves and flows around the world in rivers, pools in lakes and ponds which show up as especially magical places (the Archipelago is practically an ocean of Ecco) and flows in and out of living things in varying amounts.
The second kind of magic is Clair, Ecco's active form. When a character uses magic they are manipulating the Ecco in and around them and turning it into it's active form, which can reflect light and thus shows up as bright colors. Clair is pure energy. Used in it's rawest form it can burn, push, cut, or heal (just to name a few). If the magic user is trained, they can refine what the Clair does, such as Vaniji who hypnotizes, or Mikel who can shape rock.
Ecco is the instrument, Clair is the sound, and the third kind of magic, Wal, is the musician. Wal exists in every living thing and a few non-living ones as a core of pure magic that does not sift in and out of the body as Ecco does. In short, it is the soul. Each Wal is unique, and can be seen by special devices or the spiritually inclined. Otherwise though it can not be manipulated in the same way other magic can. Snow's arm is highly unusual in that it can not only rip a Wal from it's body but can absorb it and keep it imprisoned. It is the Wal that absorbs and gives off Ecco and manipulates the Ecco to make it into Clair.
Back to Kor and Tin-Can. A Wal cannot survive entirely exposed outside of its body. If a Wal is separated from it's fleshy form, it wraps a thin but strong wall of Clair around itself, which takes on a shape vaguely resembling its physical form. This is what Kor and Tin-Can are right now. This form gives off no heat, but is warm to the touch. It can shrink to the size of a human's fist or grow to the size of a horse (though this last requires a great deal of energy). It is weightless and can float quite easily, but obeys the laws of gravity out of habit. Younger souls (or the souls of the especially pure of heart) give off the brightest light, but all souls emit some glow, which is their Wal shining through the layer of Clair magic in their bodies, and can dim or brighten the light as they choose.
Sorry for the Wall-O-Text, hope this gives some insight into how magic on the Archipelago works. If you have any more questions, feel free to visit my new Formspring account: http://www.formspring.me/TheSilverTopHat
So many people have been asking interesting questions lately I figured I should try to keep all the questions and answers in one place.