The Castellan restraints were a brainwashing technique employed by the Sith Empire's Intelligence Service during the Cold War and Galactic War. A candidate for Castellan conditioning was primed using IX serum, distilled from the chemical dimalium-6 found on Quesh and specifically formulated for its subject. It took anywhere from three to thirty days to circulate through the subject, altering their brain chemistry to make them more susceptible; after the serum was fully absorbed, the subject was imprinted with a code word that opened the affected mind and forced them to obey the subsequent commands. The process was believed to be irreversible; Imperial Intelligence's archives indicated that the imprinting process could be used again to reset the programming, but repeated use of the IX serum would prove "inhibiting".
After the Eradication Day, the Dark Council forced the Keeper, who would shortly after be appointed Minister of Intelligence, to order the Castellan restraints for his rising-star agent, code-named Cipher Nine. While Nine's defeat of the renegade Dark Councilor Darth Jadus was commended, the Dark Council found the act of an Imperial Agent opposing a Sith Lord to be unacceptable; the alternative was to order the Agent's execution. With no choice but to obey, Keeper ordered Cipher Nine to undergo Castellan conditioning. The code word, "onomatophobia" was leaked by a Star Cabal member Hunter to Ardun Kothe, an ex-Jedi and spymaster for the Galactic Republic's Strategic Information Service, for use in Cipher Nine's undercover mission to infiltrate the SIS.