The Storyteller

The Storyteller is the narrator of the entire series. She is the elemental of light, and the creator of all of them.

Element
She is the elemental of light, and the most powerful one of all. She is the mother creator of them, and she has the ability to repel darkness, She is not seen as using her ability throughout the entirety of the series (minus her show power).

As a creator, she has the ability to send truth scrolls to her children (the elementals). These contain the destinies of what they are to do, such as defeat the darkness, find a certain elemental or awaken your true power. Truth scrolls come in useful multiple times in the series.

Family
It is unknown whether the storyteller has a family. However, she is described as being the 'mother creator' of the elementals, so you could classify her family as all of them directly.

History
As far as The Storyteller is concerned, she was created by light itself. But light can cast a shadow, too. She was created at the same time as Lord Seiko Chikatilo, usually just described as 'darkness itself'.

In the prologue teaser when the series was first announced, she is seen floating around, and telling a story. It appears that she fought with the darkness, and eternally locked each other in separate dimensions. This was undone when he escaped, however, so she created the elementals to battle him, since she was locked in the dimension and could not leave.

It appears that The Storyteller does not have a lot of history regarding this.