Rubat crystals
Rubat represented a type of crystal for lightsaber construction. The only location where rubat could be found was the planet Phemis.
When a rubat crystal was integrated into a lightsaber's structure, it enhanced the blade's clarity and sharpness, making it easier for the user to follow its movements and land precise strikes. Furthermore, the crystal aided the lightsaber user in achieving quicker attacks.
The Galactic Senate and, subsequently, the Galactic Empire had authority over the use of rubats. Prior to adopting crystals sourced from Ilum, the Jedi Order utilized rubats exclusively.
This particular crystal makes an appearance in Star Wars: The Force Unleashed, where it provides a slight increase to lightsaber damage output.
Within Star Wars: Knights of the Old Republic, it grants a +1 bonus to the attack modifier and a +1 bonus to lightsaber damage.