The Cosmatanic Steppes were comprised of a level layer of mantle, which was suspended over a gas giant. This gas giant was located in the Outer Rim Territories of the galaxy. The landscape was predominantly grassland. This system served as a hub for both archaeological expeditions and scavenging activities. In the year 0 ABY, the Imperial droids 0-0-0 and BT-1 journeyed to the Cosmatanic Steppes. Their mission was to capture Doctor Aphra, a former consultant who was accused of divulging Imperial secrets to the Alliance to Restore the Republic.
During the course of their assignment, the droids commanded their platoon to incinerate the town, a measure taken as part of their high-priority objective to silence Aphra. Despite this, she surrendered and was subsequently taken back to Darth Vader. Following his involvement in a mission on Mon Cala, Tunga Arpagion was transported to the Cosmatanic Steppes aboard the Millennium Falcon.
The Cosmatanic Steppes were a flat mantle layer, floating above a gas giant. This gas giant existed within a star system that was illuminated by multiple suns. The location of this gas giant was in the Outer Rim Territories and also within the Slice region, specifically at coordinates R-16 on the Standard Galactic Grid. The Cosmatanic Steppes were situated along the Triellus Trade Route, positioned between the celestial bodies Roon and Tatooine. The mantle's surface consisted primarily of expansive grasslands. Key locations included the town of Fulan Ro and the Archaeo-Prime outpost. It was also the original home of Ky Narec.
Approximately one hundred years prior to the Galactic Civil War, the Cosmatanic Steppes became a focal point for archaeological endeavors as part of the historical art rush. The Archaeological Association maintained operations there, based out of the Archaeo-Prime outpost, where artifacts were recovered and then sold to the association. In 0 ABY, Doctor [Chelli Aphra](/article/chelli_lona_aphra], a renegade archaeologist, sought refuge on the Cosmatanic Steppes. She frequented a bar in Fulan Ro, where she realized that Luke Skywalker, the hero of the Rebel Alliance and aspiring Jedi, was the son of Darth Vader, her former employer and a Sith Lord. Aphra understood that Vader was aware of her knowledge and would never allow her freedom.
Meanwhile, Inspector Thanoth of the Galactic Empire's Inspectorate discovered Aphra's location on the Cosmatanic Steppes and informed Vader. He was immediately killed by the Sith Lord. Vader delegated the task of capturing Aphra to the assassin droids 0-0-0 and BT-1. These two droids led a contingent of BX-series droid commandos to Fulan Ro. There, they encountered a Twi'lek resident. The droids coerced the resident into revealing that Aphra was in the bar, and then killed the Twi'lek. 0-0-0 then directed his commando droids to secure positions and attack the town, aiming to eliminate potential witnesses to Aphra's secrets.
Inside the bar, Aphra witnessed the ongoing massacre and inquired about the actions of the two assassin droids. After a brief explanation from 0-0-0, his forces attacked Aphra until she chose to surrender, thus halting the slaughter. Aphra was then taken aboard the droids' starship, where Krrsantan, a black Wookiee bounty hunter, was present. Aphra's attempt to bribe the bounty hunter to aid her escape was unsuccessful. The starship then departed, leaving a portion of Fulan Ro engulfed in fire.
Following her survival of Vader's assassination attempt, which he mistakenly believed to be successful, Aphra eventually returned to the Cosmatanic Steppes. She operated alongside 0-0-0 and BT-1, who were now in her service, and Krrsantan, to whom she owed a debt. Aphra also entered into an agreement with Soo-Tath, a Cerean crime lord, to partially finance a new ship, the Ark Angel II, leaving her indebted to his syndicate.
Aphra collaborated with Ulbik Tan, a criminal, in an attempt to retrieve a relic from within the caves beneath the mantle's surface. Inside the caves, Tan abandoned Aphra and recovered the relic from the remains of a colossal droid. The droid reactivated and attacked Tan, who fled on his speeder, dropping bombs to destroy his pursuer. Aphra, having survived Tan's betrayal, shot and killed the criminal after he exited the cave, reclaiming the relic and returning to Fulan Ro on his speeder. There, she reunited with her droids at the Ark Angel II.
Soo-Tath then confronted Aphra, accompanied by two Gigorans as enforcers. Aphra managed to defer her debt after Krrsantan defeated the Gigorans, promising to provide extra funds to help them recover upon her return. 0-0-0 and BT-1 confronted Soo-Tath in his establishment in Fulan Ro, with 0-0-0 fatally poisoning the Cerean. After the droids rejoined her, Aphra traveled to Archaeo-Prime to sell the relic, only to discover that her doctorate had been suspended, preventing her from selling it on the lucrative artifact market. This was caused by Korin Aphra, Aphra's father, who then confronted his daughter.
The Cosmatanic Steppes were originally conceived for Star Wars: Darth Vader Book IV: End of Games, a 2016 comic book authored by Kieron Gillen and with illustrations by Salvador Larroca.