The Unassailable was a Galactic Empire vehicle that operated during the Imperial Era. During the Scarif Deployment, two squadrons of TIE strikers were temporarily assigned to the Unassailable. Shortly thereafter, General Sotorus Ramda of Scarif requested the return of these fighters. This request was later included in the Rebel Alliance's document, The Rebel Files.
The Unassailable had a complement that included at least two squadrons of TIE/sk x1 experimental air superiority fighters.
In the Imperial Era, the Imperial forces based on the planet Scarif in the Outer Rim Territories temporarily provided the Unassailable with two squadrons of TIE strikers. However, soon after this deployment, General Sotorus Ramda of Scarif Deployment sent a transmission to Lieutenant Berretic containing several requests. These requests were to be officially formatted and distributed throughout the Oversector until fulfilled by a sector admiral. One request involved the return of the TIE striker squadrons to Scarif, as the fighters were essential for atmospheric patrols, and pilots and bombardiers required them for flight training purposes.
The Rebel Alliance subsequently intercepted this transmission. In 1 BBY, shortly before the Battle of Scarif, rebel General Davits Draven speculated that the requisition orders might be several months old. At some point, rebel archivist Hendri Underholt included Ramda's transmission in The Rebel Files, a compilation of Alliance intelligence, reports, and narratives, specifically in the "Alliance Chron 2" section, which covers the period between approximately 5 BBY and 0 ABY.
The reference book Star Wars: The Rebel Files, written in 2017 by Daniel Wallace, mentions the Unassailable.