While contemplating, Xin Yun took out the Taiji Diagram and closed his eyes to connect with the Four Great Sword Souls. In this battle, it was impossible for Xin Yun to deploy all four swords simultaneously, and even if he could, it would be of no use, as with his current ability, he simply couldn't lay out the Immortal Slaying Sword Formation.
As time ticked by, finally... Xin Yun opened his eyes excitedly. From the Four Great Sword Souls, he had received a wealth of information, which made him even more certain of his initial analysis and judgment.
The four Treasure Swords emitted a green light when the Executing Immortal was operational, which should correspond to the earth, as green is not the color of wind, fire, or water; only earth could possibly be green.
