Blackwing Crystal

Blackwing Crystals were unusual lightsaber crystals generated in contact with the Blackwing virus, a Sith bioweapon that transforms its victims into undead cannibals. When used in a lightsaber, they produced a dark, smokey ash blade. Such crystals were found in the caves of the Quarantine Zone during a Blackwing virus outbreak on Dathomir, during the Galactic Civil War. In 1 ABY, a group of spacers defeated a giant undead rancor in a cave below the Imperial Research and Prison Facility where the virus escaped containment and they found a collection of these crystals.

Text and facts from the “Blackwing Crystal” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.