Imps are often described as mischievous more than seriously threatening, and as lesser beings rather than more important supernatural beings. The attendants of the devil are sometimes described as imps. They are usually described as lively and having small stature.
The Old English noun impa meant a young shoot or scion of a plant or tree, and later came to mean the scion of a noble house, or a child in general. Starting in the 16th century, it was often used in expressions like "imps of serpents", "imp of hell", "imp of the devil", and so on; and by the 17th century, it came to mean a small demon, a familiar of a witch. The Old English noun and associated verb impian appear to come from an unattested Late Latin term *emputa (impotus is attested in the Salic law), the neuter plural of Greek ἔμϕυτος 'natural, implanted, grafted'.
Imps are considered to be the spawns of the devil. They serve their master (mostly the devil, but they familiar of a witch or warlock) by spreading confusing lies, which they do quite well. The main weapon of an imp is fear itself. In greater detail, imps are lesser demonic entities originating from Germanic folklore. They were not always evil back then, but always mischevious. Sometimes imps were the attendants of 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 they consider as fun and others may consider as mischevious pranks.
Later 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, but most of the time, the pranks were harmless fun, although some could be upsetting and harmful, such as switching babies or leading travellers astray in places with which they were not familiar.
Imps are considered to be invulnerable to most things, only certain objects and enchantments are capable of harming them, but they can easily kept away by 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.
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 due to their abilities and wit. 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 an extraordinary pet.
Imps are associated with Hell and fire, being a real threat for humanity and finding joy in manipulating with heat. Imps feed on the energies of people, especially arcane energies, with an exception to their master whoever it may be.
Imps have also been described as being "bound" or contained in some sort of object, such as a sword or crystal ball 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.