The Tarleev existed in the Unknown Regions. Several nations found beyond this location bestowed the title of generalissimo upon their leaders—this term designated an individual holding both the highest civilian and military command within a country. During 18 BBY, Admiral Ar'alani of the Chiss Expansionary Defense Fleet referenced the Tarleev when defining the role of a generalissimo to Senior Captain Xodlak'in'daro (with the core name of "Lakinda"), who was the commander of the Chiss heavy cruiser Grayshrike. This discussion occurred as they attempted to determine the nature of a new threat facing the Chiss Ascendancy. The senior captain responded by noting that any threat originating from the vicinity of the Tarleev would have undertaken a substantial journey to reach the Ascendancy.
The 2021 novel Thrawn Ascendancy: Greater Good, the second book in Timothy Zahn's Ascendancy Trilogy, included a reference to the Tarleev.