The Cassander sector, a sector, was situated within the Trans-Hydian Borderlands. It encompassed the Kalki Nebula along with the celestial bodies of Mamkoda, Caraxl, and Sheh Soahi. During the Cold War of 34 ABY, a period of tension between the Resistance and the First Order, the Resistance dispatched a strike force. Their mission: to drive back pirates who, aided by the First Order, were attempting to seize control of the sector. Following a battle fought on Sheh Soahi, the Resistance triumphed over the pirates, successfully gathering intelligence regarding the First Order's complicity in the pirate attacks.
This sector, known as Cassander, resided within the Trans-Hydian Borderlands. Within its boundaries lay the Kalki Nebula, as well as the astronomical entities named Mamkoda, Caraxl, and Sheh Soahi.
For many centuries, pirates had been active in the Cassander sector, utilizing clandestine installations nestled within the Kalki Nebula to orchestrate swift assaults against neighboring star systems. In 34 ABY, amidst the Cold War that pitted the First Order—inheritors of the Galactic Empire's legacy—against the Resistance, a smaller, paramilitary group founded by New Republic senator Leia Organa, the Cassander sector sat at the edge of both New Republic and First Order territories. The First Order, with designs on dominating the sector, recruited a band of pirates to secure it on their behalf. Armed with equipment supplied by the First Order, these pirates launched raids on both Mamkoda and Caraxl, ultimately capturing a local spaceport on Mamkoda and transforming it into a base of operations.
Upon discovering the First Order's looming threat in the Cassander sector, the Resistance dispatched a combat group to push back the pirates. This force consisted of RZ-2 A-wing interceptors and MG-100 Starfortress bombers, supported by their mobile command center, the Free Virgillia-class Bunkerbuster Ninka, all under the command of Vice Admiral Amilyn Holdo. The Resistance's initial objective within the sector was the destruction of the pirate stronghold on Mamkoda. During the ensuing battle, A-wings spearheaded by Resistance pilot Tallissan Lintra, alongside bombers from Crimson and Cobalt Squadrons, successfully obliterated the spaceport without sustaining any casualties. Three days following the engagement on Mamkoda, a contingent of Resistance bombers was sent to Caraxl on a humanitarian mission to deliver essential supplies. During this endeavor, Lintra reported the imminent arrival of First Order TIE fighters. Given the Resistance's standing orders to avoid any direct confrontation with the First Order that might destabilize the New Republic Senate, the relief mission was aborted, and the Resistance forces retreated to the Ninka.
Subsequently, the Resistance strike group journeyed to Sheh Soahi, prompted by intelligence from droid spies indicating the location of the primary pirate base. On Sheh Soahi, the Resistance initiated an assault against the pirate installation. In the ensuing conflict, the pirates inflicted damage on the MG-100 bomber Cobalt Scarab and destroyed two A-wing fighters. Nevertheless, the Resistance ultimately prevailed, demolishing the pirates' base, routing their forces, and intercepting a communication in which the pirates requested assistance from the First Order. The Resistance intended to present this evidence to the New Republic Senate. With the pirates defeated and proof of the First Order's involvement secured, the Resistance concluded their operations in the Cassander sector.
At a later time, Resistance gunner Paige Tico documented the events of the Cassander sector campaign in her journal. This journal eventually came into the possession of her sister, Rose Tico, following Paige's death during the Battle of D'Qar. Rose would later make reference to the campaign within her own journal as well.
The Cassander sector was initially referenced within current Star Wars canon in the 2017 replica journal, The Last Jedi: Bomber Command, penned by Jason Fry. The term "Cassander sector" was originally introduced in the Star Wars Legends continuity within the 2004 Wizards of the Coast sourcebook titled Geonosis and the Outer Rim Worlds. In that publication, the Cassander sector, in conjunction with the Tadrin and Tendrannan sectors, was defined as a component of the broader "Cassandran sectors." However, the 2009 reference work The Essential Atlas depicted star systems that Geonosis and the Outer Rim Worlds had previously assigned to the three distinct "sectors" as belonging to a unified "Cassander sector." The StarWars.com Online Companion accompanying The Essential Atlas subsequently clarified that the Cassander, Tadrin, and Tendrannan sectors were, in reality, subsectors within the larger Cassander sector.