Once the Lantern is placed, it will reveal 3 lines of codes on the roof. These lines will each be made up of symbols. You must figure out from this code which three signs to punch with the Galvaknuckles, one from each line. The order doesn't matter.
In the tunnels above the town there are five signs, and the phrases on each sign correspond to a code sequence shown below. Each is 17 characters long if the player counts the spaces as a character. The players need only decode the first letter of each sign as all five are different.
DRY GULCHER SHAFT
GROUND BITER PITS
BONE ORCHARD VEIN
You can use the above reference to figure out which three signs you must punch, or if you would like to decipher the whole sequence, you can use this guide:
So for example, say that you have the following codes appear on the wall:
The first line begins with:
If we line up the white chalk with the guide, it fits into the top right. If we then line up the red chalk with one of the three letters within, we get the letter "G". The only sign that starts with a G is Ground Biter Pits, so we know that is one of the signs. You can follow the same process with the rest of the code to decipher it, and with the next two lines to figure out which signs to punch.
Now that you know the sign names, locate them in the tunnels above. Once you have found them, in any order, punch them with the galvaknuckles in quick succession to spawn the wisp and begin the next step. Note: It is recommended to read the next step before you end the current step.