Pit Fiends can be one of the most devastating monsters in the game, though they do not attack Prisoners directly. Instead, they radically change the board by turning existing tiles, quite suddenly, into Pits.
Pit Fiends are placed like any other tile. Once placed, Pit Fiends immediately turn every tile in a diagonal line from it (including Key, Gate, and Monster tiles) into Pits, even if separated by empty spaces.
The Pit Fiend itself then becomes a Pit. Luckily, Pit Fiend attacks DO NOT wrap around the board, but end at its edges.
Any player who has a Pit created beneath them by a Pit Fiend immediately Falls, out of turn. Normal turn order then resumes.
Pit Fiends are especially terrifying towards the end of the game, where their attack could well remove your last Gate or a critical Key tile.
In the example, BLUE places a PIT FIEND. All the spaces outlined in red are in range, stopping at the board’s edge. All tiles in this range become Pits instantly. GREEN immediately Falls, placing their token along the board edge. The Wax Eater becomes a Pit and is no longer a threat. The Gate becomes a Pit, potentially ending the game if is the last gate. If BLUE places the Pit Fiend on the other available space, they can dramatically reduce the impact. Place with care!
(Try adding a 3rd Pit Fiend for an even harder challenge.)