The coming of the Avatar of the Light Side was predicted in the Avatar's Prophecy, written by the Dark Lord Izenghar.
The Avatar of the Light Side was supposed to be a man who would carry the true power of the Light Side of the Force, and with it, he would harvest the power to destroy evil and to defeat darkness.
The only Avatar of Light that history has record of is Hei-Ri Devon, a human male Jedi Master; who was born to fight Darth Daggus, the Avatar of the Dark Side.