The "Quiescence" is the communications dead zone in the Creterakian Empire, with the planet Creterak at its center. The Quiescence technology significantly dampens or completely eliminates all frequencies across the radio spectrum, including microwave and ELF frequencies.
The Quiescence was originally limited to the planet Creterak. Until the Creterakians achieved FTL tech in 2639, no one knew of the sentient race's existence. This was due to quiescence technology that blocked all Creterakian communications from escaping the planet. The Creterakians were able to remain hidden from potential colonizing species until they were able to properly defend themselves from potential aggression.
The Quiescence now covers a massive area equal to most of the Creterakian Empire's territory. It is believed the Creterakian Orbital Stations (Emperor 1 through Emperor 5) contribute to this zone of silence.