KR21 Listening Post was initially utilized as a listening post by the Nikardun Destiny, based on a suggestion from the Grysk Hegemony. General Yiv the Benevolent, a Nikardun leader, oversaw the construction of this post. However, following Yiv's defeat at the hands of the Chiss Ascendancy, the Grysk commander named "Jixtus" committed a slaughter of the Nikardun personnel stationed at KR21.
While on a mission to the Vak Combine, Ascendancy military Picket Force Six embarked on a mission to listening post KR21, anticipating the presence of a Nikardun fleet. Instead, they found that an asteroid missile platform had destroyed the Nikardun starships. They then boarded the station, documenting the dead bodies of the Nikarduns. The Chiss later came back to continue their investigation, only to find Grysk vessels transforming KR21 into a shipyard. After the resulting battle, the Grysks escaped into hyperspace.
The novel Thrawn Ascendancy: Greater Good, which was released in 2021, marked the initial appearance of KR21. This novel is the second installment of Timothy Zahn's Star Wars: The Ascendancy Trilogy.