The Undead Rancor was a large bull rancor that could be found in the caves of the Quarantine Zone on Dathomir. It was mutated by Imperial bioweapons Project I71A, codenamed "Blackwing". This creature guarded several Blackwing crystals, which could be used to produce a smoke-colored lightsaber blade. The Undead Rancor was eventually defeated by a band of spacers.