Looking at this line, Di Tou's eye couldn't help but twitch, as he suddenly recalled his experience the last time he was at the trial grounds. Thanks to a hint from Qing Xin, he had learned that the well water wasn't just water, but was actually a powerful supplementary material for tempering one's Spiritual Sense!
By dipping one's Spiritual Sense into the well water, they would feel an exceptional chill, which would 'solidify' their Spiritual Sense, allowing it to stretch further without breaking apart and causing harm to the cultivator, in such a way one could keep extending their Spiritual Sense deeper and deeper into the well, increasing its durability and practicing their flexibility.
Such a treasure could help a cultivator skip many years of diligent practice and the consumption of many valuable materials.