Firkrann Firkrann crystals represent a type of lightsaber crystal that was relatively dense, and these crystals were extracted from the planet named Rafa V. When installed, the crystal gives the weapon an electrical property, making the lightsaber particularly effective against droids. Historical records indicate that the Dark Lords of the Sith were known users of these crystals.
During Revan's exploration of Sith Lord Tulak Hord's tomb, he discovered a Firkrann crystal, potentially one that Hord had utilized within his own lightsaber.
In Star Wars: The Force Unleashed, this specific crystal appears as a lightsaber crystal which can occasionally imbue the lightsaber with the power of Force lightning.