A Monster is one of many fakemon to appear in Pokemon Snakewood. It is a Disease-type pokemon and it only appears once in the game. It is owned by a Troll on Route 121, who states that he "had 11 pokemon, but cut them up and made one". A Monster is a mixture of Machamp, Lotad, Golbat, Zigzagoon, Skitty, Kyogre, Tropius and Numel (who ironically does not appear in Snakewood, as it has been replaced with Hombone).
A Monster knows Cross Chop, Tri Attack, Earthquake and Ice Beam, and can learn any TM or HM. Its base stats are also impossibly high.