[Source] The Mantle of the Force was a powerful crystal rediscovered by Suvam Tan and possibly used by Revan. It added a cyan color to a lightsaber. Revan purchased this crystal from Suvam Tan near the end of his search for the Star Forge, as well as another legendary crystal, the Heart of the Guardian. He discovered that when placed in a lightsaber, its properties altered depending on the other crystals the lightsaber carried, making it more powerful in the areas that the other crystals improved; though it always enhanced Force abilities.