The Fairy King is the King of Fairies, husband of the Fairy Queen and father of Bracken and four daughters. He commanded the male Fairies during his time of reign. During that time, the Fairy Queen assigned Astrids to guard the Fairy King. However, the Demon King Gorgrog attacked the Fairies and 'killed' the Fairy King. This tragedy could have been prevented if the Astrids had not lowered their guard out of arrogance.
Because of his death, the male Fairies disappeared and the Imps were born. He was mentioned several times in Secrets of the Dragon Sanctuary and Keys to the Demon Prison, and it was revealed that he was chained to Gorgrog as a trophy, dragged along in Zzyzx by the Demon King for centuries. After the Demon King got slain by Kendra Sorenson using the legendary sword, Vasilis, the Fairy King was brought back physically by the Sands of Sanctity and began to recuperate.
In the first book of the Dragonwatch series, the Fairy King protects Seth from Dragons chasing him by temporarily allowing him to enter the Fairy Realm. He then sends him to Fablehaven and states that he is eternally gratefully and owes Seth endless favors for bringing the sword that ended the Demon King and the Fairy King's suffering.