When humans breathe, we inhale O2 (a molocule comprised of 2 oxygen atoms) along with various other gasses like Nitrogen, that have no real effect on us. However, when we breathe out we emit CO2. However, we don\'t have big lumps of carbon in our lungs, so where does it come from?
Ourselves. When the red blood cells exchange the oxygen, they take the spent O2, now bonded to a Carbon atom given by one of our cells, and release it as CO2.
This is how we can suffocate ourselves if we have a plastic bag over our head. Eventually, we fill the bag with our spent oxgen. Ironically, there could very well be a large portion of oxygen left in the bag, as lungs are a very inneficent way of breathing (only 10% of what we exhale or some # close to there is CO2.)
It could very well be the same with Kran, where if you encased them in a bag they
would eventually suffocate due to the lack of oxygen. However, instead of Carbon, they put Silicon in the place, thus releasing SiO2... or sand. However, this is very slow, as:
Silicon still supports oxygen linkages, so Kran breathe much more slowly than other races, enabling them to happily breathe underwater
They don\'t have lungs and they dont need them; they breathe through their skin as if it were a massive gill.
They\'re basically eroding away as time passes, however slowly. To stop this from happening, they would have to digest silicon to replace whatever they lost due to their \"breathing.\" They would then, obviously, eat things with silicon and various other elements in them. It is also noted that their \"kitchens\" are like chemical labs, which means that whatever they eat could certainly be highly-dangerous to other species, if not in the end result, then in the creation of the food.
They would most likely eat by grinding the \"food\" into sand-sized particles, then let them slide down to their \"stomach.\" As far as we\'re concerned, that\'s where the digestive tract stops. After the \"food\" has been digested by the kran\'s stomach acids (perhaps strong enough to break chemical bonds) it would then most likely be absorbed through the stomach walls and then, under capillary action, simply \"seep\" to the kran\'s skin, where it replaces what parts were lost.
As far as the movement, it could very well be that the kran DO have muscles, but not in a biological sense. Perhaps they have a material used as a muscle that expands and contracts 100 or even 1000 times more then a normal peice of metal does when heated, which would allow them to eat their food and move their tough skin. For a brain... Well, think of a computer\'s CPU! However, this \"computer\" brain would not operate on C++, but instead use chemical markers and various other elements and molocules of matter for memory and action dictation; but always with silicon as the main component.
As for reproduction, they may simply \"seed\" like a flower does. A small area on their body grows to resemble a simple kran, and the new kran simply drops off and begins to feast on whatever kran food there is nearby. Perhaps even dropping the \"seed\" kran into a pile of sand and chemicals used to develope their body. Haha. A good kran spa could be considered a pool of quicksand with various rare and color-tinted crystals growing nearby.

Well... there goes 20 minutes of my life. Oh well. :rolleyes:
[for further referance, think of a Kran\'s arm as a tree trunk. In the center is the main \"vein\" of the body part, that contains all the nutrients and materials needed for growth. Everything else is \"dead\" like a tree\'s bark, even though the bark of the tree still serves the purpose of protecting the vein of the limb. As the kran grows, the limb heals, albiet very slowly. If i were to compare Kran to anything, it\'d be a tree.
As a side note - Any sort of catalyst or enzyme that speeds the chemical reaction between silicon and oxygen would litterally turn Kran into dust. 8o Thus, if a Kran were to meet a feeble, old [insert race here] and the old person were to throw a container of this catalyst at the Kran, it\'d be instant death.]