Imps are usually intimidating, as their physical form compromises the fears and thoughts of its summoner into being. Some Imps take the forms of literal monsters, hulking, slavering demons that the mage must summon all his courage even to approach. Some are small and unassuming things, using the forms of terrestrial animals. Some even appear human. But regardless of their form, they are always confronting their summoner with moral conflicting tests and trials.
As beings born out of space, Imps are perfect for scrying as they don't need sympathetic bonds in order to find someone. They are also able to help mages to overcome mental blocks that hinder their development of certain Arcana.