The Battle of Byss occurred some time after the end of the Clone Wars, when the Alderaanian Resistance launched its final attack on the forces of the Sarlacc Project.
The battle
By capturing an orbiting space station, a team of infiltrators were able to deactivate the defenses of Byss, allowing the smuggler fleet of Lady Alya Aldrete to fly into the Super Star Destroyer prototype's reactor core, destroying it and ending the threat.
Appearances
Sources
Dawn of Defiance: Gamemaster Primer on Wizards.com (original site is defunct) (First mentioned)