In the fourth book, The Opal Deception, Opal Koboi, who had been lying in an institution in a catatonic state, escapes with the help of pixie twins Mervall and Descant Brill, and begins plotting revenge against Julius Root, Holly Short, Foaly, and Artemis.
In the fifth book, The Lost Colony, Artemis works with the People to recover a young kidnapped demon imp from the 12-year-old child prodigy Minerva Paradizo.