Every Judge Magister that the party encounters throughout Final Fantasy XII seems to be dual-wielders and can combine their main and off-hand weapons into a single weapon consisting of two edges/blades. Gabranth himself wields two swords – the longer one, named Chaos Blade, in his right hand, and the shorter one, named Highway Star, in his left hand.
When using his special attacks, Gabranth briefly combines his weapons then disassembles them before launching the attack.
The party fights Gabranth twice in the game -- once at the Third Ascend of Pharos and once on Sky Fortress Bahamut.
Gabranth has a tendency to cast Protect at the beginning of the battle and target Basch if he is in the party. A special cutscene will also be played if Basch is in the party when Gabranth is at 50% HP, after which Gabranth will become immune to magicks for around 2 minutes. Gabranth uses a special attack in this battle called Guilt, which is a single-target attack and deals heavy physical damage to the target.
Again, Gabranth has a tendency to target Basch if he is in the party, and a cutscene will play when Gabranth is at 50% HP. After the cutscene, Gabranth will likely cast Renew, which fully recovers his HP. He will also immediately cast Innocence after casing Renew, which is an area attack that does phsycial damage to multiple targets when they surround him. When his HP drops to 25%, Gabranth’s defense will increase and will cast Innocence in quick successions.