These are the giant chunks of land that you live on. No-one knows what purpose there is to their slow dance of drifting together, or floating apart (if they do, they aren’t telling). Each can host an ecosystem of plants and animals, farms and towns, though as their size ranges from a pebble to a mountain the amount of life each can support is very variable. Additionally, the life of a fragment is the subject of much uncertainty, as they rise from the Mists, get colonized and lived on for many years, and then seem to lose whatever it was that was driving it and fall back down to the depths.
In many cultures and families, however, methods have been found of interfering with the motion of the fragment through the careful placing, removal and shifting of mass around the fragment, resulting in a change in the height and direction of a fragment’s flight. Another important role is that of the one who monitors the ‘health’ of the fragment, so others can be warned if the fragment is likely to return to the Mists soon.
You will have heard of and possibly even encountered many kinds of fragments very different to the norm, from giant crystals to fragments which seem to distort the laws of nature. The placement of the fragment makes a big difference as to what kind of life it can support; those too close to the storms and the mists will suffer blazing heat or energy-sapping cold respectively, not to mention all the other strange effects that getting close to either one will have.