The dual-phase lightsaber is an extremely rare variant that incorporates an adjustable blade of two distinct lengths, often of different colours. It is usual for the second length to be longer, if not double, the length of the ordinary blade, though there is nothing preventing the user from aligning the crystals in order for the second blade to be of appreciably shorter length.
The use of a dual-phase lightsaber should not be taken lightly and they typically require intensive training to be used efficiently. Like many of the more common lightsaber variants such as the double bladed variety a dual-phase lightsaber can be more a danger to the adherent than his opponent if he is inexperienced in its use. This is especially true for extended blades where the additional length can make the weapon ungainly and awkward to wield properly during combat. In the past many who have built dual-phase lightsabers have come to reconsider their usefulness and taken to using the extended blade more for purposes outside combat than during a duel.
The weapons are rare primarily due to the rarity of the focussing crystals required in their construction. The variable phase emitter means the crystals must be able to handle much greater power outputs and be constructed with a level of precision far greater than even that needed for an ordinary lightsaber. Examples of dual-phase lightsabers have been used by Jedi and Sith alike including Exar Kun, Darth Vader and Corran Horn.
Requirements
Due to the difficulty in aligning the crystals for a Dual-Phase Lightsabers, only a Dark Jedi Master can attempt to build one.