In my friend and my mythos, Wyander, we have four classes of dragons. Each dragon has two forms, human and dragon, and the change between them is controllable as long as one form isn't favored above the other and used all of the time. In that case the neglected shape will force its way into being at least once a week. Sno is a Niveus, the lowliest, and smallest of the evil dragons. Barely the size of a horse it poses no real threat at all, and conicidentally is one of the most common dragons.