C129 Subject to human control

After about an hour, Gu Shiyi finally found a hidden pile of sand a kilometer outside of the city.

Pushing aside the sand, a long copper tube extended out into the distance, with only a pitch-black patch of sand to be seen.

Gu Shiyi pressed her ear to the mouth of the copper pipe, and could even hear the sound of the air flowing inside.

Huyan Bie was indeed as he had expected