Sector 21C (also known as Sector Malurian[1]) was a region in or near Federation space, a sector located in the galaxy's the galaxy's Beta Quadrant, a location on star charts used by the Federation in the 23rd century.
History and specifics
Sector 21C included Maluria, where the probe
was discovered and compelled to self destruct. (ST reference: Spaceflight Chronology)
Maluria was located in the Beta Quadrant in the general vicinity of Nausicaa, Regulus and Yridia. (ST reference: Star Charts)