Things that the guardian giants built, even if it were just a ventilation duct, looked like a tunnel in the eyes of ordinary humans.
Perhaps Hao Ren's lunatic superior was guarding her employee. It may also be that the goddess of creation was protecting her own daughter. The group made it to the ventilation duct under the nose of the festered monster without being detected.
The power of the Mad Lord had infested almost everything one Amantir, including the temples and its ancillary facilities. But the contamination did not affect the regular operation of facilities such as energy and lighting systems. The vents of the ventilation ducts still worked, the internal circulation system and lighting also functioned as usual, and it was quiet inside the ventilation duct. Had it not been for the depressively chilly atmosphere, and the strange smell in the air, Hao Ren would have forgotten that he was moving in the lair of the Mad Lord minions.