Game demons are arguably one of the most encountered types of demons. Most any story about a Ouija board, or game that plays its self contains such a creature.
The demons themselves are formless in real space, and often are tiny in the abyss, but that doesn't mean they are powerless. They are keen soul thieves, and cruel beyond compare. They also have a host of psychic abilities such as mind reading, thought projection, and the ability to cause their victim to hallucinate.
The ability to read minds is by far their greatest tool, allowing them to sucker you in with promises you want, or keeping you drawn in to write some wrong it claims to have committed.As well, the price for losing is your soul, and quite obviously, death.
Commonly these are found in old board games, if it is a two player game they will commonly take the form of the second player in a game with possibly the highest stakes. if it has multiple players, it will prey on all of them, hoping to lead them to violence against one another. However, they have been breaking into electronic media. Luckily they don't seem to have the same power over optical media, and all digital media lacks physical form and thus can not be possessed so in a few years this might not even be a concern anymore.
The common game demon will often start of simply toyign with its prey. showing signs that soemthing is not as it seems, maybe game pieces are wrong (headless knights), or things in the game don't normally exist (Hellscape Terrace), to wrong audio cues. Over time however, it starts to show its real face. outwardly taunting the victim with horrible things that no other could know. Often trying to make it seem as though they have been responsible for every bad thing in the victim's life, but if they win here their luck might turn around. This however, is completely a lie.
Luckily, they are bound by rules. both by the rules of the game, which can be broken if the player consents such as money for landing on park place and other home rules, and by ones defined by some other power. Firstly they can not control the player. they can not read the player's mind to predict their next move, and they can not outright kill the player once the game has begun. Breaking these rules is often met with instant backlash from an unknown source and will lead to the eventaul downfall of the demon if they are not careful.
This is also not to say that they can not game around these. There has been cases where a game demon in a chess board trained their prey to play chess over years. They became an expert chess player under the tutelage of the demon, however, once it sprang its trap, knowing only the demon's tactics they were quickly beaten. The motivation for this however, is unknown. It is suspected that they rave challenge in games, and to simply beat a child or novice is no fun.
Defeating a game demon is not overly difficult. Destroying its vessel will return it back to the abyss, and destroying it within the proper confines will kill the demon outright as they can not exist in our world independently.
However, once you have engaged a game demon in its game, expect a mental onslaught forcing you to face your greatest fears, and if you do not possess the mental fortitude to persevere as your dead relatives tell you everything they hate about you while murdering your mother, it is best to just destroy your next game demon before seeing what makes it tick.