At the start of the Galactic Civil War, Mother Grotrugga was the leader of the convent.
Shortly after the destruction of the first Death Star, when Imperial forces were forced to leave the Vodilux Star Cluster in which the asteroid was located, to replace units destroyed during the Battle of Yavin, a team of Imperial Scouts was sent to the asteroid in the guise of Rebel agents in the hope of creating mistrust and perhaps hate between the nuns and the Rebel Alliance so that the Rebels could not use the asteroid as one of their bases. Though they were given full clearance to land and meet with Mother Grotrugga, and were even allowed to present their fake Alliance ultimatum stating that the nuns turn over full control of the asteroid to the Rebel Alliance and allow them to rearm it, the nuns (or at least Mother Grotrugga) knew that they were in fact Imperial agents. So, when they slew Grotrugga, she made no attempt to stop them, allowing her physical body to die, becoming a Force ghost.
This temporarily stunned the other nuns all over the base, perhaps from sensing her death through the Force, which in turn allowed the Imperial Scouts to attempt an escape. Eventually, however, the nuns gained their senses and attempted to stop the Imperials from leaving by simply blocking the corridors (as they were large enough to do so, being mostly Gamorreans). However, they soon heard the voice of the departed Mother Grotrugga telling them not to oppose the group and allow them simply to leave. The nuns obeyed their former sister's order without question, allowing the group of Imperials to leave without any further problems.
After this incident, Mother Grotrugga continued to appear to the convent in her new ghostly form, first informing them that it was the Galactic Empire rather than the Rebel Alliance who murdered her, and also giving her successor spiritual guidance. Because of this, the nuns invited the Rebel Alliance to make peaceful use of the asteroid as soon as Imperial forces left the area. They still did not allow the Rebels to arm the base, but the Alliance had never wanted to do so anyway. Many Rebels took short breaks on the asteroid to revitalize themselves both spiritually and psychologically and to recover from the trauma of war. Though the Imperials continued to send units to deal with the nuns, they always ran into inexplicable problems, such as motivator breakdowns, white plastic armor fatigue, and computer viruses. No one was ever hurt in these attempts, but the ships were always forced to turn back.
The "Nuns of G'aav'aar'oon" is a play on the 1961 film The Guns of Navarone.
The chapter on adventure design in Star Wars: The Roleplaying Game, Second Edition, Revised and Expanded mentions conflict between the Empire and an order of monks drawn from an educated Gamorrean elite class as a possible adventure scenario. However, these monks live in a castle on a planetary plateau rather than in an asteroid fortress, and the example gamemaster ends up rejecting the idea of the monastery being near an old Jedi chapter house.
The "Nuns of G'aav'aar'oon" is a play on the 1961 film The Guns of Navarone.
The chapter on adventure design in Star Wars: The Roleplaying Game, Second Edition, Revised and Expanded mentions conflict between the Empire and an order of monks drawn from an educated Gamorrean elite class as a possible adventure scenario. However, these monks live in a castle on a planetary plateau rather than in an asteroid fortress, and the example gamemaster ends up rejecting the idea of the monastery being near an old Jedi chapter house.