From the introduction: Water. Earth. Fire. Air. Since the dawn of time, these elements have been in balance, their powers waxing and waning but ever returning to harmony. For ten thousand years, mankind has followed these elements, devoting themselves philosophically and spiritually to them, and in turn gaining control over them. Water Tribe, Earth Kingdom, Fire Nation, and Air Nomads - each gives the potential to master one of the four elements, allowing the person so empowered to move, shape, and sculpt that element with their body and will through sacred techniques known as the Bending Arts.