Todd Jensen writes...

Have you ever read Katharine Briggs's "An Encyclopedia of Fairies"? It's a very good dictionary of faerie-folk and faerie elements in legend (don't worry; it all deals with the fay as portrayed in primary sources), containing entries on practically every aspect of them. In particular, it's got entries on many of the familiar fay in the series (Oberon, Titania, Puck, the Banshee, the Lady of the Lake, Odin), ones that you planned to get into the series (Queen Mab and Morgan le Fay), and related elements (Cuchulain, iron, bells, time in Fairyland, A Midsummer Night's Dream), etc.