Origin
The king and ruler of the Flame Kingdom, and the father of Flame Princess, the Flame King is a giant fire elemental, clad in heavy armor. He believes himself and his fire people naturally evil. It is because of this belief that he agreed to his daughter Flame Princesses in a lantern, at the request of Princess Bubblegum. Flame Princess is then released by Finn and Jake, after which she falls in love with Finn, thinking him to be a prince.
Creation
The Flame King is an Adventure Time character created by Pendleton Ward. Originally appearing in the animation Adventure Time (voiced by Keith David), the character would be adapted to the Adventure Time comic series as well, appearing in Adventure Time #10.