The Hammer is a heavy weapon that is slow to swing, but deals decent damage.
It is the only way the wanderer can unlock doors with a hollowed hexagon icon. To open these pathways, smash the button on the floor with the hammer in hand. The pathway should remain open for all future runs.
The Hammer can be found on Floor 5 inside of a room that requires opening via an arrow-switch at a range (Verification needed).