SKUL is a criminal organisation which is the main enemy of M.I.9 who are either attempting to take over the world (in that episode) or are funding some one else to do it. SKUL is run by a shadowy leader only referred to as the Grand Master.
SKUL was originally a division of KORPS, but the Grand Master betrayed them to M.I.9 so that he could break SKUL from KORPS and run it himself. The name SKUL later became an acronym for "Secret Kriminal Underworld League".
- The identity of the first in command (Mastermind, Grand Master) is not revealed.
- The identity of the second in command (Crime Minister, Jade Dixon-Halliday) is revealed.
- The leaders are male and rarely go into the field.
- The executive leaders are female and constantly go into the field.
- Grand Master (SKUL Leader)
- Jade Dixon-Halliday (Second in Command, M.I.9 Double Agent)
- Kloe: Clone of the Mastermind trained by SKUL (captured by M.I.9)
- Zoe: Clone of the Mastermind trained by SKUL (now M.I.9 Agent)
- Grand Mistress (Former SKUL and SKUM Leader)
- Sally Moreau (SKUL Scientist)
- Sonya Frost (SKUL Secretary and ex-TV Weather Girl)
- Chad Turner (SKUL and CIA Double Agent)
- Silas Fenton (SKUL Agent and Inventor)
- Vanessa Zietgeist (SKUL Beautician)
- Zero (The Grand Master's Nephew)
- Paloma Duvere (Headmistress of SKUL Academy)
- Leah Retsam (The Grand Master's Grandchild)
- Suki (SKUL Academy Student)
- Anita Blackwell (SKUL Academy Student)
- Lorenzo Ferrago (Fashion Designer)
- Maximus Fiticus
- Nora Braithwate
- Brian Gainsborough
- Agent X
- Wallis Inpersonator
- Elmer Pantry
- Toby Bleach
- Troy Greek
- Quillian Pendrix
- SKUL is a reference to SPECTRE from James Bond.