Guest Stars Donna Kimball voices Aughra Keegan-Michael Key voices The Ritual Master Gugu Mbatha-Raw voices Seladon Mark Hamill voices The Scientist Benedict Wong voices The General Caitríona Balfe voices Tavra 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