There are many kinds of evil outsiders in the game, most notably Demons (traditionally chaotic evil) and Devils (traditionally lawful evil). Nearly all evil outsiders in Harvest Moon are called "Demons" and their collective language is "Demonic". Not only this, but although well over 99 percent of all Demons are evil, traditional "Devils" are not always lawful and traditional "Demons" are not always chaotic.

Lawful, neutral, and chaotic demons generally fill the same roles in The Pit as their good or neutral counterparts do on the surface of the world. Demons have a central power base (often contested, however) with a network-style power structure that extends down and up through The Pit and even across the face of the world. The Demons definitely have their factions, but these usually consist of a wide mix of Demon types, each faction loyal to a particular leader or council. The structure of evil outsiders is very dangerous in the Harvest Moon Campaign world due to this collusion between the different races. However, it also makes them more approachable. From a certain point of view, this makes them yet more dangerous, especially to those who choose to follow the straight and narrow. Good and Neutral characters can often find themselves deep within the machinations of the Demons that they no longer have the option to climb out ever again.

Note that evil elementals are usually not considered Demons in the traditional sense, however those who truck with Demons do share this distinction regardless.