The Montrosa Islands constituted a lengthy archipelago situated centrally within the Montrosa Ocean on the world of Reytha. Their diminutive size rendered them unsuitable for farming, and their isolated location discouraged colonization, making these islands a perfect location for Rebel Alliance aerial bases and ship-building facilities.
The existence of a Rebel contingent in 0 ABY required an invasion by Galactic Empire troops under the command of Darth Vader with the aim of eliminating the rebels.
The Montrosa Islands were initially featured in the Darth Vader storyline within the 2001 computer game Star Wars: Galactic Battlegrounds. This same storyline was also present in the 2002 game expansion Clone Campaigns.