From publisher blurb:
Nestled between the warring energies of the elemental planes, Everglow is bathed in these angry washes of primal force. Some people respond strangely to this energy, becoming vessels for its might and becoming fueled by power beyond their plane. These are the elementalists, and they're ready to change the landscape of battle.
Included, besides a new 20 level class, are class archetypes, new feats, and support for alternative multiclassing, to add a dash of planar power to your existing character!