Fairy King/World Tree

The Fairy King, or World Tree, is Beth's father. He is the one who watches and rules over the Fairy World.

Personality
As a tree there is not much depth to him at first. He is sentient, being able to call to his daughter and show her visions. He displays immense power and is willing to sacrifice his own life to seal great evils and protect his daughter and the citizens of the Fairy World. He is gentle and approachable as both tree and human and cares deeply for Beth.

Appearance
The King of the Fairy World takes the appearance of a towering massive tree, hence the name World Tree. It is revealed later in the series that the tree form is used to recover and conserve energy.

However, at times, he is able to take the form of a man. In his human form he appears as a tall slender man. He has long green hair, pale skin, and a gentle face.

Background
The World Tree is stated to have watched over and nourished all in the Fairy World since the realm’s very creation. With this, one can come to the conclusion that the Fairy King is an ancient being.

Trivia

 * The Fairy King's actually name is not revealed during the anime series.
 * One possibility, would be Yggdrasil. A tree from mythology, often called the "World Tree".