THE ELEMENT OF LIGHT
When the eight elementals focus their powers together, they form the power of light which they use through the conduit, the Silver Dolphins.
Learn more about the mysterious Silver Dolphins and why the book is titled after them by reading book 1!
Because the elements in union create the power of light, whenever an elemental draws upon the dark instead of their light they fall into elemental rage. Learn more about that in book 1 and here.