What is this suggestion related to (eg. Website / Launcher / The game itself / etc. ):
Description: Add an aggressive 1HP and 1 ATK bug that roams at some parts of the city as a reference to the culvert. Literally a town cockroach which is easy to kill, but always spawns again.
Killing that mob could be the start of a quest that leads the player to the culvert.
A permanent quest could be placed on a bulletin board about an infestation, the leader of the “Prontera Cleaning Party” gives a task of finding from where those bugs are escaping from, and then the culverts are accessible to that player, or something like that xD