Null Cannons, a type of superweapon, were created by the Galactic Republic around the time of the Cold War. These weapons functioned by emitting energy blasts that could render enemy technology, such as starships, completely inoperable. One such prototype was part of the Republic Navy contingent stationed at Hoth; it was lost on the planet when the fleet crashed during the battle against the Sith Empire.
The lost weapon remained on Hoth until a Republic Military operation, spearheaded by Admiral Revald, aimed to recover it for use against the Sith. Aided by a prominent Republic citizen, the endeavor was complicated by the presence of local White Maw pirates, who also sought to claim the weapon. Captain Sero, a pirate leader, was at the time making copies of the Null Cannon, intending to equip his forces with them. Sero attempted to barter the cannons to the Republic, but a sudden strike team led him to believe the negotiators had betrayed him, and he attacked, but was defeated.
Following the defeat of Captain Sero, the player(s) are presented with a choice: destroy all the Null Cannons, allowing the Republic to spend months rebuilding the prototype (the light side option), or attempt to preserve them all (the dark side choice).
For players aligning with the Republic in the Star Wars: The Old Republic: Onslaught story, General Daeruun mentions that Admiral Revald had several Null Cannon prototypes made, but they were too unstable for deployment in the Battle of Corellia.