What does the switch inside the fire do?

There's a fire in a room and I used my mega douser to put out the fire, I went inside and pressed the action button and I heard something change inside the dungeon, can somebody tell me what it did ?

Solution 1:

Congratulations, you've unlocked the secret room that will take you to the Oubliette. It's a secret level between the first and second floors. Look for a new room on your map.

If you can't find a weapon that fires something wet, you can also roll a water barrel into the room to put the fire out. This takes a bit more work, but you can import a barrel from another room if you're so inclined.

It takes two keys to unlock the trap door down to the Oubliette, so I hope you saved up! If not, there's always next time...

Do note that falling down the trap door means you'll leave this level completely, so if you want to, say, kill the boss first for a chance at guns/hegemony credits, do so beforehand.