Lin Mu remembered reading about this kind of rock in the Memoirs of the Lost immortal. The man had also encountered it before and was actually blocked by it. That was one of the instances when he had been trapped.
He was exploring the depths of volcanic tunnels and it had collapsed, trapping him inside. On one side was fuming magma and on the other side was the Earthen Depths Obsidian.
At that time the Lost Immortal was at the Dao Shell realm. He could not go through the magma as he did not have any spirit tool or skill that would be able to resist its heat and breaking through the Earthen Depths Obsidian was also not an option.
The man was trapped in there for over a year before he managed to escape. He had suffered a lot during that time and had grown weary. But even then he did not manage to break through the Earthen Depths obsidian.
