He is the king of Raregroove and the head of Demon Card in the Rave Master franchise.
King's real name is Gale Raregroove whose friend is Gale Glory. King and Gale were born on the same day of the same year. Both men created Demon Card to fight demons, but their friendship started to sour. About 15 years after Gale has left Demon Card, King gets a visit from Gale. At first, King asks Gale if he is coming back to Demon Card. Yet, King frowns when he hears that Gale's goal is to stop Demon Card due its use of Dark Bring. King tells Gale to go home. When Gale Glory calls the authorities to arrest Demon Card, the authorities decide to kill everyone including Gale's wife and son. This causes King to kill Sakura Glory to make Gale feel the pain that he felt. As heir to the Raregroove kingdom, he feels that destiny will always bring him loneliness and despair due to his birth on the converging day. (Complete details on his origin story is under Tower of Din Arc)
Gale Raregroove (King), who is created by Hiro Mashima, has no current information on what inspires the author to create him. He first appears in Rave Master episode 19. His Japanese voice actor is Tesshou Genda, and his English actor is Peter Lurie.
"I will show you the sadness of losing your family."
King - Episode 35 - to Gale Glory before killing Sakura Glory
King is Gale's best friend until his family was massacred because of Gale and Slade's actions. He resorts to using Dark Bring and strengthening Demon Card. Before meeting Haru Glory during the Tower of Din arc, he believes that he will always be destined to be alone and in the darkness. After Haru and Gale beat King, he has a change of heart and decides to use Overdrive on Demon Card headquarters.
King appears in as mysterious figure who orders Sieg Hart to take down Haru Glory, and he gives Reina orders to kill Sieg Hart if he shows any sign of betrayal.
King appears after Haru has wiped out the demons and Gale who has appear as well. He clashes sword with Gale Glory, and after the shockwave, King reveals Black Zenith to Gale and Haru. When the tower gets hit by lightning and morphs, King explains how the converging day connects his enemies and him. He explains that on this day, Rave is created and Overdrive occured. On this day, he and Gale are born and then 20 years later, he and Gale met and created Demon Card. After his explanation, King heads inside the tower towards the top. Since King cannot move from this spot due to Enclaim ritual, he uses a Dark Bring, Gate, to summon the Five Palace Guardians. He tells them to kill Haru and the others except Gale Glory which he will defeat personally. After the Palace Guardians separate Haru from Gale, King meets Gale again and the two start fighting.