Rhamsis Callo was an Outer Rim Territories planet located in the Danjar sector. It was the homeworld of the Force-sensitive and militaristic Schenor species, which allowed the Galactic Empire to construct a base on the planet despite remaining neutral in the Galactic Civil War. During that conflict, a team of Rebel Alliance agents delivered a young survivor of an Imperial massacre of a Schenor colony to Rhamsis Callo. When the Schenor noble B'karitz learned about the massacre, he led an insurrection that attempted to drive the Imperial forces off Rhamsis Callo.
Rhamsis Callo, also known simply as Callo, was a terrestrial planet located in the Rhamsis Callo system, a part of the Outer Rim Territories' Danjar sector.
During the Galactic Civil War between the Galactic Empire and the Rebel Alliance, the Schenor species of Rhamsis Callo maintained their neutrality. However, the Schenor government did sign a treaty with the Empire allowing the latter to begin the construction of a base on the planet. At some point during that conflict, a group of Rebel agents rescued the young Schenor A'kazz from a massacre the Empire carried out at a Schenor research station. The Rebels transported the child to a nearby Alliance base, where Commander Luke Skywalker, believing that A'kazz's testimony of the Empire's actions could help persuade the latter's species to align with the Rebellion, subsequently tasked the group with delivering the young Schenor to his nest-guild on Rhamsis Callo.
Arriving on the planet, the Rebel team traveled on a local reaction car to the province where A'kazz's nest-guildmaster, B'karitz, resided. During the journey, Imperial agents attempted to waylay the Rebels by staging vehicular chases, stealthy attacks, and shootouts at wayside accommodations. After the Rebel agents finally brought A'kazz to B'karitz—and convinced the mistrustful noble of their good intentions—the latter telepathically interrogated the child. What he learned from A'kazz made B'karitz vow to prevent the further construction of the Imperial base on Rhamsis Callo, break the treaty with the Empire, and drive the Imperials from the planet.
The nest-guildmaster, accompanied by both his nest-warriors and the Rebel group, traveled to the partially constructed Imperial base, where B'karitz summoned the Empire's ambassador and declared to them that the treaty between the Empire and the Schenor was null and void and that the Empire's presence on Rhamsis Callo was to end immediately. Although the Imperials pretended to cooperate, they used a secret alarm to summon troopers, who then surrounded and attacked B'karitz and his force. The Rebels and the nest-guildmaster boarded the former's starship, from where B'karitz summoned aid from other Schenor nobles. The Alliance agents then engaged the Imperial forces, including fleeing starships, in further combat. The Rebels disabled and boarded the ambassador's cruiser, which then allowed them to send the diplomat back to Rhamsis Callo to face Schenor justice.
Rhamsis Callo was the homeworld of the Schenor, a species of eight-foot-tall Force-sensitive and telepathic felinoid sentients. The Schenor society, organized into units known as nest-guilds, had also stratified into tiers of lowly peasants and middle-class as well as all-powerful nobles. The natives had a government representing the species in relations with off-world visitors—of whom they were traditionally distrustful—and their homeworld's units of territorial administration included provinces.
The militaristic Schenor lived according to a rigid code of honor, and martial arts were held in respect in their society. The transportation technology of Rhamsis Callo's natives included reaction cars, a type of powerful and fast, but also noisy, inefficient, and dangerous, ground-effect vehicles. At some point, the Schenor established a remote research station colony off-world. In turn, after the species established contact with the Galactic Empire, an Imperial contingent including an ambassador and troopers as well as several starships was dispatched to Rhamsis Callo.
The Schenor architecture of Rhamsis Callo, which included the Rhamsis Callo Spaceport at Chafflock, consisted of red sandstone buildings decorated with geometric ornaments made of earth-tone clay. In addition, during the Galactic Civil War, the Galactic Empire was constructing a military base on the planet.
Rhamsis Callo was first mentioned in the roleplaying game adventure idea "The Silent Witness," which was authored by Ken Rolston and published in the 1987 rulebook for the first edition of West End Games' Star Wars: The Roleplaying Game. This article assumes the scenario plays out as described. "Twinkle, Twinkle Little Star, How I Wonder Where We Are," a 1990 roleplaying source article published in Voyages SF 13, placed the planet in the "Tion" sector. Since that article was released outside of the Lucas Licensing process, its canonicity within the Star Wars Legends continuity was never confirmed.
The 2009 reference book The Essential Atlas subsequently placed the Rhamsis Callo system, and therefore Rhamsis Callo itself, in grid square N-19, far from the Tion Cluster and the trio of sectors into which it was divided. The StarWars.com Online Companion to the book further overrode the Voyages SF 13 placement by establishing that the system was situated in the Danjar sector.