Bondar

Bondar was a type of crystal used in the construction of lightsabers, also known as lightsaber crystals. An asteroid in far orbit around the Alderaan system was the only known source of bondar.

When set in a lightsaber's crystal chamber, bondar allowed the wielder to stun an opponent with the blade.

Behind the scenes
In the video game, Star Wars: Knights of the Old Republic you may use this crystal as a lightsaber upgrade. It has a 25% chance to stun your opponent on hit for one round.

There are also two legendary crystals: The Heart of the Guardian increases the stun effects to last for two rounds while the Mantle of the Force alters the properties.