The Constancia mission represented an endeavor by the Alliance to Restore the Republic aimed at transporting Gamine, a Constancian leader possessing crucial details regarding a strategy to protect her people from Imperial annihilation, back to her homeworld.
The Constancians were a race originating from the planet Constancia characterized by their telepathic abilities. This telepathic talent was an innate characteristic of their species, a rare phenomenon. As the Galactic Empire gained dominance, the Constancians concealed their powers, fearing potential exploitation by the Empire. Their concerns proved justified. While Gamine, the Constancian leader, was away from their home, the Empire uncovered the truth about the Constancians and demanded that they utilize their telepathy to serve the Empire. Refusal meant the imminent destruction of their home planet.
In desperation, Gamine reached out to the Alliance to Restore the Republic. The Rebels devised a strategy to rescue the Constancians, but during this process, the Empire established a blockade within the Constancia system. Luke Skywalker, C-3PO, and R2-D2 were assigned the task of delivering Gamine and the Rebel plan's details to Constancia, navigating through the Imperial blockade.
The Rebel vessel carrying Gamine, Luke, and their companions was attacked by an Imperial Star Destroyer, seemingly bringing the mission to an abrupt end. Anticipating the destruction of their ship, Luke Skywalker evacuated in a lifepod with Gamine. He deactivated C-3PO and R2-D2 and launched them into space, attached to a signal beacon programmed with specific instructions. Unbeknownst to the Imperials, a hidden outpost existed within the icy ring surrounding Constancia, manned by the loyal Constancian warrior Sharlee. Sharlee detected the lifepod and rescued Luke and Gamine, but the heavy Imperial presence in orbit around Constancia trapped them in Outpost 8.
Luke's foresight proved valuable. He had programmed the signal beacon to activate the two droids and itself upon detecting the departure of Imperial vessels. Luke also sent a distress signal to Han Solo, who promptly arrived in the Millennium Falcon accompanied by Chewbacca and a reluctant Gyla Petro. Solo rescued the droids, evaded the Imperial blockade, and reached Outpost 8 in time to implement Luke and Gamine's plan.
Han and Sharlee boarded the lifepod from Luke's destroyed ship and launched with a distress signal that led the Imperials to believe they were Luke and Gamine. They were quickly captured by Imperial boarding craft 356. However, instead of the expected stranded individuals, the Imperial Navy troopers on board encountered Han and Sharlee in battle armor. Enhanced by the armor's capabilities, the two managed to seize control of the ship.
The second part of Gamine's plan was initiated. Luke, Gamine, and the others departed in the Millennium Falcon, heading towards Constancia. Imperial TIE Advanced x1s and TIE/LN starfighters quickly pursued them, but upon receiving a message from Boarding Craft 356 instructing them to retreat while the boarding craft intercepted the Millennium Falcon, they complied. By the time the Imperials realized that Boarding Craft 356 had been hijacked, it was too late. The Rebels were close enough to the planet for the Constancian ground defenses to assist them, enabling them to escape safely to Constancia.
With Gamine's return to Constancia, the Rebel mission achieved its objective. Gamine possessed the crucial information regarding the Rebel strategy to save the Constancians. Although their struggle had only just begun, they had secured their first victory, and the Constancians warmly welcomed the Rebels upon their arrival.