Fairies, like angels, are a topic on which there is a huge diversity of views. I was re-reading The Fairies in Tradition and Literature by Katherine Briggs, which covers a great deal of ground, considering the origins of faeries in ancient myths, as tutelary spirits, from literature and other sources. One area she does not really explore, though, is that of the fairies in the grimoires. Fairies in different forms have turned up during the research I have been carrying out for the last seven years with Stephen Skinner. An example of the diversity of fairies in the grimoires came to light in Sloane MS 3825 (seventeenth century), which we published in The Keys to the Gateway of Magic, which discusses the types of fairies associated with different parts of the landscape, such as Napta in flowers, Hamedes in meadows, Oreads in mountains and Potamides in rivers.
Another related seventeenth century manuscript, Sloane MS 3824, contains more such material, and talks about calling on fairies to reveal hidden treasure. In particular there is reference to the fairy king Oberion. This is not an isolated incidence, and he occurs in a number of other old grimoire manuscripts, indicating his populariy and that he was fairly well known. Significantly however, as I discovred when I was working on material about this for The Book of Treasure Spirits, Oberion refused to talk to priests who conjured him up, whereas magicians or cunning folk were more likely to receive a reply. Not only does this emphasise the willingness of magicians and others in the renaissance to conjure fairies, but also their interchangeability of roles with angels, demons and elementals.
Reginald Scot in The Discoverie of Witchcraft (1684) also discussed fairies in the context of grimoire material, though he also mixed it up with a lot of contemporary beliefs about witches. The connection between witches and fairies is one which has crossed over into folklore far more noticeably than the grimoires. However as time goes by more is sure to be revealed on how fairies and the grimoire magicians interacted, and who knows what other such revelations may come out!