Beyond the caverns lies the ultimate challenge: 'The Underworld' (d-u). This realm is home to 'Demons' (z-D), 'Forgotten Beasts' (z-F), and the legendary material 'Adamantine' (d-a). Venturing into the Underworld is a one-way trip for most fortresses, as sealing it off after breaching is extremely difficult. Only attempt this with a well-established, heavily defended fortress and a powerful 'Militia'. The rewards are immense, but so are the risks of utter destruction.
