In the long quest of Polluted River Quest, you’ll be asked by the NPC Mosman Time to find a chest that is holding a key somewhere in Clock Tower B1, the only clue is the chest is near the Holy Statue.
If for some reason, you cannot find the chest. Here is where you can find it. The Chest is just on the left top corner of the map.
Once you reach this area, you’ll find the Secret Chest Chamber Treasure Chest.
Take the key and you can now proceed to Clock Tower 2F and give it to Tina Member of Clock Guardian.
That’s it! Hope this quick guide help you.