Guest Stars Donna Kimball voices Aughra Mark Hamill voices The Scientist Keegan-Michael Key voices The Ritual Master Benedict Wong voices The General Caitríona Balfe voices Tavra Gugu Mbatha-Raw voices Seladon Jason Isaacs voices The Emperor Simon Pegg voices The Chamberlain Victor Yerrid voices Hup Harris Dickinson voices Gurjin Neil Sterenberg voices The Scroll Keeper Awkwafina voices The Collector Harvey Fierstein voices The Gourmand Toby Jones voices Librarian Mark Strong voices Ordon Helena Bonham Carter voices All-Maudra Natalie Dormer voices Onica Suzy Eddie Izzard voices Cadia