Opal Koboi is a fictional character from the Artemis Fowl series - a set of six fantasy novels written by Irish author Eoin Colfer. After the character's May 2002 introduction in the second book in the series as a supporting antagonist, Colfer again used Koboi as the main antagonist in the fourth and sixth book of the series, giving her the status of arch-enemy to the main protagonist, Artemis Fowl II.