Originating from Germanic folklore, the imp was a small lesser demon. It should also be noted that demons in Germanic legends were not necessarily always evil. Imps were often mischievous rather than evil or harmful, and in some regions they were portrayed as attendants of the gods.
Imps are often shown as small and not very attractive creatures. Their behavior is described as being wild and uncontrollable, much the same as fairies, and in some cultures they were considered the same beings, both sharing the same sense of free spirit and enjoyment of all things fun. It was later in history that people began to associate fairies with being good and imps with being malicious and evil. However, both creatures were fond of pranks and misleading people. Most of the time, the pranks were harmless fun, but some could be upsetting and harmful, such as switching babies or leading travellers astray in places with which they were not familiar. Though imps are often thought of as being immortal, many cultures believed that they could be damaged or harmed by certain weapons and enchantments, or be kept out of people's homes by the use of wards.
Imps were often portrayed as lonely little creatures always in search of human attention. They often used jokes and pranks as a means of attracting human friendship, which often backfired when people became tired or annoyed of the imp's endeavors, usually driving it away.
Even if the imp was successful in getting the friendship it sought, it often still played pranks and jokes on its friend, either out of boredom or simply because this was the nature of the imp. This trait gave way to using the term "impish" for someone who loves pranks and practical jokes. Being associated with hell and fire, imps take a particular pleasure from playing with temperatures.
To this end it came to be believed that imps were the familiar spirit servants of witches and warlocks, where the little demons served as spies and informants. During the time of the witch hunts, supernatural creatures such as imps were sought out as proof of witchcraft, though often the so called "imp" was typically a black cat, lizard, toad or some other form of uncommon pet.
Imps have also been described as being "bound" or contained in some sort of object, such as a sword or crystal ball. In other cases imps were simply kept in a certain object and summoned only when their masters had need of them. Some even had the ability to grant their owners wishes, much like a genie. This was the object of the 1891 story The Bottle Imp by Robert Louis Stevenson, which told of an imp contained in a bottle that would grant the owner their every wish, the catch being that the owner's soul would be sent to hell if they didn't sell the bottle to a new owner before their death.
Imps can be found in art and architecture throughout the world, usually carefully and painstakingly hidden under the eve of a church or the foot of a ceramic cup, so they can only be found by the most interested and observant of people.
Imps may be described as fairies in some cases but in most cases the Imp in question is an evil spirit or demon. They frequently appear in children's stories such as 'Silvia' in which she is followed by a black Imp. Since their time they have become more overlooked as not many people actually know what they are.
Imps are also portrayed as a servant to those of fey and magical being, such as wizards. Because of this reason, they are commonly used in games as minions, such as World of Warcraft, The Legend of Zelda, RuneScape, etc..