It is first found on the floor in the first room of the tunnels. The mace is used here as part of a puzzle to open the door, along with an Obsidian sword and Obsidian knife. To open the door, the mace must be placed on the western pedestal and the sword on the eastern pedestal.
It is also one of the weapons found on the floor of the fourth room of the tunnels. It must be used on the northeastern pedestal as part of the puzzle to open the door.
A mace is used once again in the seventh room of the tunnels. It should be placed on a pedastal marked "Ket" and "Hur".