The Mon Calamari Rangers functioned as a resistance movement on Dac around the year 137 ABY. Their objective was to safeguard Mon Calamari refugees and fight against the genocide targeting their people, which commenced with the Massacre of New Coral City.
Prior to Admiral Stazi's successful capture of the Imperious, the Mon Calamari Council implemented contingency plans in the event they were penalized for the starship's theft. However, these preparations were prematurely halted when Darth Krayt, the Dark Lord of the Sith and Galactic Emperor, demanded the extermination of 10% of the planet's inhabitants as a warning to the galaxy.
Teaming up with Imperial Knight Treis Sinde, the Mon Calamari Rangers endeavored to shield their people until the Empire was expelled from the planet. Under Sinde's direction, the Rangers confronted the Sea Leviathan during the Battle of Devil's Crevasse. After Master Sinde went back to Bastion, Jedi Master Asaak Dan took his place.
In anticipation of the evacuation of the planet's civilian population, which was organized by Admiral Gar Stazi of the Galactic Alliance Remnant, the Rangers, assisted by Master Dan, seized the floating city of Heurkea, confronting a small detachment of stormtroopers in the process.