Cunning of Tyranus
Tyranus's Cunning was a distinctive lightsaber crystal that produced a red blade, and it took its name from Count Dooku, the Human leader of the Separatist movement, who was also known as Darth Tyranus in his role as a Sith Lord. The color of a lightsaber became red when this crystal was incorporated into its construction. If a Force-sensitive individual attuned it, it transformed into a focusing crystal that could only be used in a lightsaber built by that specific person.
Behind the scenes
In the 2003 Star Wars Galaxies MMORPG, Cunning of Tyranus was a special lightsaber crystal that players could find. Jedi characters could equip their lightsabers with this crystal to add extra heat damage to the weapon. This crystal was found through the "Rare Loot System," that gave players a chance to acquire increasingly rare items from any defeated enemy.