The Expeditionary Library, alternatively called the Chiss data library, was a substantial subterranean library. It resided beneath the ice sheets covering Csilla, the capital planet belonging to the Chiss Ascendancy. This repository contained documents and works resulting from the Chiss Expansionary Defense Force's explorations within the Unknown Regions. To safeguard against data loss from ice storms, the majority of the content was translated into Basic and preserved in written form. In 28 ABY, a combined Galactic Alliance–Imperial Remnant group, under the leadership of Jedi Master Luke Skywalker, journeyed to this Chiss library. Their objective was to discover the location of Zonama Sekot, a sentient world, and they successfully identified its location within the Klasse Ephemora system.
Far from the Chiss city of Ac'siel, the Expeditionary Library, also known as the Chiss data library, was situated in a distant area of Csilla, the capital world of the Chiss Ascendancy found within the Unknown Regions. The library was a secure facility located deep beneath Csilla's ice layers, accessible through a set of imposing, robust doors. Resembling the dimensions of a docking bay, the Expeditionary Library was rectangular and featured four levels of walkways lining the walls, reachable by steep staircases. Suspended from the library's ceiling by cables were yellow lights. The main floor was divided by numerous rows of shelves, creating narrow passages between them. A sizable square table, crafted from snowwood, stood at the Expeditionary Library's center, offering seating for at least twenty individuals. The air within the library was still, warm, and devoid of moisture.
Contained within the Expeditionary Library were mission logs, records of contact, anthropological studies, and xenobiology papers. These materials originated from the Chiss Expansionary Defense Force's exploration of the galaxy's Unknown Regions, all preserved in book format. This was because technological data storage was vulnerable to destruction by ice storms, resulting in the absence of holoscreens within the library. Given the entirely written nature of the library's contents, specific methods aided in subject searches, and the library's cataloging was meticulously maintained. While much of the library's text had been translated into Basic, some remained in Cheunh, the language of the Chiss species.
The Expeditionary Library's existence dates back to 27,000 BBY. Throughout their formative years, Chiss individuals assimilated fundamental knowledge from the library's volumes following extensive education. It held the most comprehensive collection of data concerning the Mnggal-Mnggal entity, including the coordinates of its homeworld, Mugg Fallow, and all available details regarding its origins. Some considered Lorgrombo, a Lugubraa elder, as a low-tech counterpart to the significant Expeditionary Library.
By 28 ABY, during the Yuuzhan Vong War when the extra-galactic Yuuzhan Vong were invading the galaxy, the Chiss Expansionary Defense Force had been exploring the Unknown Regions for centuries. Consequently, the library contained potentially billions of pages of information. In that year, a Galactic Alliance–Imperial Remnant team, led by Jedi Master Luke Skywalker, visited Csilla during their search for the [hyperspace](/article/hyperspace-legends]-traveling, sentient planet Zonama Sekot.
The Chiss Ruling Families and the Chiss Expansionary Defense Force granted the team access to the Expeditionary Library for a period of two days, along with a guide named Tris. The team members became some of the few non-Chiss individuals ever permitted to enter the Expeditionary Library. In their search for Zonama Sekot, they traced references to the wandering planet through the Chiss Expansionary Defense Force's reports and faced a skirmish with Chiss factions opposed to the changes resulting from external influence. With the assistance of Wynssa Fel, a young Csilla resident, the team sought the living planet's current location. They searched for systems that had acquired planets within the past sixty years, employing an algorithm Fel created on a holopad. After that approach failed, switching the search to moon acquisitions revealed Zonama Sekot's location: the Klasse Ephemora system. The Expeditionary Library's role in the Yuuzhan Vong War was documented in a historical document published in 36 ABY by the Historical Council of the Galactic Federation of Free Alliances.
The Expeditionary Library was featured in Force Heretic II: Refugee, a 2003 novel by Sean Williams and Shane Dix that was part of The New Jedi Order series.