Once the home of the Carosites, Carosi XII was a planet situated in the Outer Rim Territories. The Carosites established a colony there in 200 BBY, subsequent to the destruction of their former world, Carosi IV. Renowned for its therapeutic centers and tourism, it drew a diverse array of travelers due to its advantageous location along a major trade route. Further, Carosi XII openly supported the Rebel Alliance, making it a sanctuary for free-traders, Alliance operatives, and personnel of the New Republic.
The Eurae Mountains formed a perimeter around Carosi XII, with the remaining landscape largely consisting of plains and extensive glaciers. The planet's only significant body of water was the Avuae Sea, which served as a central point for Carosite society and culture. Due to its high mineral concentration, the Avuae Sea never froze, and its waters were considered invigorating by Carosites and others capable of enduring its intense cold.
Ongoing volcanic activity contributed to the formation of Carosi XII's most sought-after tourist attraction: the hot springs located near Newlife Point, celebrated for their inherent healing properties. Tourists could travel from Newlife Point to the crystalline cave housing the hot springs using either an underground train or a leisure boat.
Astronomers accurately forecasted the transformation of the star Carosi into a red giant. In anticipation of this event, terraforming projects were initiated on Carosi XII. These efforts proved successful, and following the engulfment of their original homeworld by Carosi, the Carosites relocated to the twelfth planet, which, despite now being the seventh planet, retained its original designation.
During the Galactic Civil War, Polo Se'lab held command of Rebel forces stationed on the planet, with Sayer Mon Neela serving as the base's tactical expert. Later on, Omo Taj, the Carosite leader, authorized the New Republic to establish a New Republic outpost on a mountainside near the northern coast of the Avuae Sea. Balderik Rajana was the commander of this outpost.
Planets of the Galaxy, Volume Two, along with its reprint, The Star Wars Planets Collection, indicates that Carosi XII possesses only a single moon. However, the novel Planet of Twilight mentions a factory located on Carosi's larger moon, suggesting the existence of multiple moons. As of yet, no official explanation exists for this inconsistency.