Starting with book 2, with the exception of book 31, a bonus mini-adventure was added at the end of each book featuring a character that is encountered during the main adventure or that lives events linked to it. These bonus adventures are written by various authors under the supervision of Dever himself. Illustrations for these bonus adventures were done by Nathan Furman (books 2 to 11 and 17), Richard Longmore (books 12 to 16 and 23), Stephanie Böhm (book 18, 20 and 21), Aljosa Mujabasic (book 20), Hauke Kock (book 19, 22 and 24), Richard "Nerdgore" Sampson (book 25 and 26) and Adélaïde Euriat (book 29). No illustrations were made for the bonus adventure in book 30.