After returning to the Azure Dragon Town, Ling Han asked the villagers some questions again. Only then did he realize that he had been slightly misled.
One could indeed find Heavenly Dragon Bone Ashes in that canyon. Moreover, that canyon was also the best place to search for Heavenly Dragon Bone Ashes. However, this was entirely time-dependent.
During an entire year, there would only be three or so days when the canyon would become calm, without a single gust of wind. At that time, it would be extremely easy to enter and search for Heavenly Dragon Bone Ashes. After this time, however, the canyon would become chaotic with violent wind. In fact, even Immortal Palace Tier elites would cry in pain if they were struck by the flying rocks.