"Barrier Replacements"
People who entered the slum other than the patrol guards and the town's citizens could only leave through the exit and the exit was so far away from the entrance.
The trapped monsters naturally could not leave even though they found the exit, but the unlucky intruders could still go through the exit to directly leave Acacia underwater town.
They could even leave without having to go through the mist wall that they had to go through before entering the range of this underwater town.
Ainsley and the others didn't know about this, so they rushed to the entrance of the slum, but to their surprise, no matter how hard they tried to pass through, it felt as if they bumped into some kind of solid wall!
They could not see the wall, but these experts immediately knew that they bumped into a barrier.