In the eighth book, "The Last Guardian", Artemis must save humankind by stopping the crazed pixie Opal Koboi. Opal kills her younger self (who followed Artemis and Holly to the present in the sixth book) to gain enough black magic to open a magical gate, which has been under the Fowl Manor for a millennium, and so release the Berserkers (ancient fairy warriors). Then Artemis must fight his brothers, who have been taken over by the Berserker souls. He sacrifices himself at the conclusion of the book to trigger an ancient spell that disperses Opal and her various fairy spirits, but since his spirit was human (apart from some traces of fairy magic from Holly's borrowed eye), his essence endures at the location of the spell long enough for Holly and Foaly to clone a new body for him and transfer his soul into it. Although the process leaves him with missing memories, the book ends with Butler, Holly and Foaly immediately beginning work to restore them.