Opal Koboi is Artemis Fowl's nemesis. Opal is a pixie who once filled a role similar to Foaly's. However, Opal has gotten it into her head that she should become empress of the world. To this end, Opal has done many things to make herself many powerful. The last thing Opal needs to make herself powerful is the brain fluid of a lemur. However, older Artemis tricks her out of the lemur so she goes into the future and makes Artemis' mother ill in an attempt to get the lemur when older Artemis brings the lemur back to save his mother. In the end, Artemis outsmarts Opal, but then she disappears.
