Null Cannons were a type of superweapon developed by the Galactic Republic by the time of the Cold War. It functioned by firing energy blasts that completely disabled enemy technology such as starships. A prototype was present amongst the Republic Navy fleet at Hoth before they crashed on the planet during the battle against the Sith Empire.
There they remained until a Republic Military initiative on the planet led by Admiral Revald sought to reclaim the weapon for use against the Sith. This operation was aided by a notable Republic citizen but faced opposition from the local White Maw pirates that intended to claim the weapon for themselves. Pirate Captain Sero was involved with making numerous replicas of the Null Cannon during this time with the intention of distributing them amongst his forces. Sero attempted to negotiate trading the cannons to the Republic, but a surprise back up strike team made him believe the negotiators had betrayed him and attacked but was defeated.
After defeating Captain Sero, the player(s) have the choice of destroying all the Null Cannons, leaving the Republic months to rebuild the prototype (light side dialogue), or try to preserve them all (dark side choice).
For players who side with the Republic in the Star Wars: The Old Republic: Onslaught storyline, General Daeruun mentions that Admiral Revald has several Null Cannons prototypes created but are too unstable to be used in the Battle of Corellia.
After defeating Captain Sero, the player(s) have the choice of destroying all the Null Cannons, leaving the Republic months to rebuild the prototype (light side dialogue), or try to preserve them all (dark side choice).
For players who side with the Republic in the Star Wars: The Old Republic: Onslaught storyline, General Daeruun mentions that Admiral Revald has several Null Cannons prototypes created but are too unstable to be used in the Battle of Corellia.