After entering Dillmoor, visit each area at least 150 times. This will unlock the special monsters that are in each area, such as the special Landworm in the high chambers of Robelia Castle (before you open up the upper area with Emma), and the flying dragon or land dragon in Dillmoor, and the land dragon and two other special monsters to fight in Gaslin Caves. This will work better if you have an accessory with an addition to Occurrences. These monsters will not show up until you go through Dillmoor, Baulson's Quest, and Celepaleis.