Outer Rim Patrol Squadron 21 or RimPatRon 21 was assigned to patrol the Western Reaches of the Outer rim. Based on a planet called Saaristo. While the planet is fairly lightly populated by Imperial standards, it is rich in mineral resources, with a thriving mining economy. Emperor Palpatine ordered a base to be established to protect the world and the subsector it resides.
Originally RimPatRon 21 consisted of:
1 Gozanti Class Cruiser
4 Lambda Class Shuttles
3 VT-49 Decimators
12 Tie Fighters.
The base also hosted a garrison of:
250 Imperial Army troopers.
24 Speeder Bikes
After the Battle of Yavin Rear Admiral Grigori Lensoven was the base's commanding officer, however years after Yavin Lensoven refused to believe the Emperor and Lord Vader were dead, and the base, it's equipment, and the planet suffered as Lensoven refused to make any move that would make the subsector or the planet self sufficient. As a result there was growing unrest, not only on the planet, but within the base. Commodore Alistar Jenks eventually mutinied, having Lensoven imprisoned, and announcing himself the planet and sector's military governor. Alistar is a well respected officer who commands the trio of Decimators that shouldered the lion's share of the squadron's patrol duties. The Gozanti cruiser and Lambda class shuttles were primarily for transporting troops where they were needed through out the subsector.
As a result of Alistar's reputation, pilots, and other officers who had served with him or under him, had flocked to Saaristo when they heard he had taken control.
This resulted his forces growing to include a second Gozanti class cruiser, bearing 4 TIE Interceptors, several dozen more army troopers, and most notably, a Raider class corvette.
Alistar still favors the Decimators he spent most of his career with, often carrying his flag on one, but due to practicality the Raider is most often his flaship.