Nextor
this was one of the many crystals used by the ancient Sith Lord in the construction of a lightsaber. It was believed to have given the wielder the ability to cause a greater amount of damage with a blow from their lightsaber. It was also thought that a nextor crystal caused an opponent to feel fear or apprehension when faced with the lightsaber. Nextor crystals were found almost exclusively on the planet M'haeli.