A Research from Wikipedia
Imps are usually 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.
 Imps in folklore
Some accounts of imps treat them as capable of being turned to good, because they are so desperately lonely they would do almost anything — even commit good deeds — to have a committed friend; however, it is regarded as almost impossible for any imp to fully forsake its "impish" ways.
The Ancient Greek demigod Pan has some features in common with an imp, but this is unlikely to be a direct connection, since the imp concept probably belongs to Germanic rather than Hellenic tradition. However, imps are sometimes described as fond of music, and capable of being charmed into making a promise to aid, and "do good" in that manner through music — though there is always likely to be some mischievous trick to be attached to the barter.
Imps were the common name given to familiar spirits that served witches in the middle ages. Imps were usually kept inside artifacts such as gemstone pieces or vials and summoned for service by magics. An example of such an imp is one that was supposedly under the service of the Alchemist Paracelsus, who supposedly kept one locked inside a crystal in the pommel of his sword.
 Imp Guardians
Imp Guardians are a larger, smarter, more adept at the arcane arts version of the Imp. They serve as the protectors of the Imp's home realm, hence the name 'Guardian'.