Under the guidance of the radiant light, Lin Yi flew into the passage above, similar to his first entry into the Dan God Secret Realm, he suddenly found himself enveloped in darkness, with only the guiding light still shining around him.
In such a situation, ordinary cultivators naturally couldn't see anything, but through the Eye of Emptiness, he could see the spatial turbulence surrounding him.
Using the standard method of ascension, one would be protected within the Ascension Tunnel and wouldn't be harmed by the turbulence, while those who stow away would need to traverse these spatial turbulences.
Presumably, those who returned to the Lower Realm had to pass through these spatial turbulences as stowaways, as there were no regular means for a cultivator to safely return to the Lower Realm from the Upper Realms.