Quan Chi, Ashrah, Sareena, Kia, Jataaka, Siann, Mika and Sora are the most well known examples of demons. They can hide their appearance underneath a human façade, but otherwise seem to be the same as Oni. Quan Chi was originally an Oni, until he became a demon with his mastery over sorcery and magic. Siann, Mika and Sora were originally lifeless corpses until Quan Chi saved them. Other generic demons have appeared in Mortal Kombat: Shaolin Monks as regular minions that players fight later in the game.
Different classes included the Demon Wards, Demon Warmonger and small Imps. Other classes of demons that wore armor and carried weapons are Demon Archers, Demon Captains, Demon Generals and Demon Handlers.
In Mortal Kombat (2011), guest character Freddy Krueger appears as the first Dream Demon to appear in the series, with his powers and abilities coming from the his resurrection in Hell, allowing him to manipulate and control the dreams of his victims. Despite this, it is possible to bring Freddy to the real world, which in turn renders his powers, and ultimately his Immortality, completely useless.
- There was going to be another class of the Netherrealm's high level demons called the Elder Demons, including the character Baphomet, mentioned in the Krypt and Kontent gallery of Mortal Kombat: Deadly Alliance. These dark creatures are similar to the Elder Gods, only less powerful.
- As explained in their endings in MK 2011 and Armageddon endings respectively, Smoke and Hsu Hao may in actuality be some manner of demons themselves, with Smoke's variation being known as an Enenra.