During Emperor Palpatine's reign over the Galactic Empire, a period spanning from 19 BBY to 4 ABY, the Imperial Navy maintained the 15th Deep Core Reserve Fleet as a reserve fleet. This fleet was under the command of Admiral Yzu.
The Empire considered the planet of Empress Teta a crucial stronghold because of its valuable resources and its location as a gateway into the Deep Core. Officially, the 15th Deep Core Reserve Fleet's Star Destroyers and support ships were documented as conducting customs patrols to suppress smugglers and pirates in the region. However, the fleet also had the responsibility of managing a hyperspace interdiction checkpoint located on the sole known hyperspace route connecting the Empress Teta system to the Deep Core's interior.
The 2016 Star Wars: Force and Destiny roleplaying game sourcebook Nexus of Power, created by Fantasy Flight Games, included the 15th Deep Core Reserve Fleet in the new Star Wars canon. The 1995 Star Wars: The Roleplaying Game boxed set The DarkStryder Campaign by West End Games was the first mention of it within Star Wars Legends continuity.