The moment Yan Zhen showed the intention to run away, Lu Li had made plans accordingly. He sent someone to secretly destroy that tunnel. The one to perform the task was not a human being, the supreme king of the Waters Region.
That supreme king was at the Semi-God Realm. He was taken into the outer hall of the Wicked Bead by Lu Li when they were at the Waters Region. Lu Li secretly let him out. The supreme king came to the tunnel in advance. When Yan Zhen arrived, the tunnel just happened to be ruined.
Usually, the spatial tunnel would remain stable when not being attacked. It could last for several years. However, once someone came to attack at the tunnel, it would become unstable. Space would shrink and eventually, the entire tunnel would collapse under such pressure.
The moment the tunnel fell apart, Yan Zhen was paled. Never once had he felt so vulnerable, so close to death.