A dual-phase lightsaber represented a type of lightsaber incorporating at least two kyber crystals. This design enabled the blade to be made longer or shorter while engaged in combat. A notable instance was Darth Vader's lightsaber, which realized this capability through the inclusion of two kyber crystals.
By the era of the Clone Wars, dual-phase lightsabers were largely obsolete, relics from a more brutal time. These lightsabers incorporated supplementary focusing crystals, which, when activated, could surprise an adversary. This class of weapon permitted the user to shift the crystals to a different configuration with the press of a button, thereby altering the length of the lightsaber's blade. Typically, this momentary change in blade length would cause a lapse in the opponent's defense, creating an opportunity for the wielder to capitalize on their opponent's disorientation.