Many hold that the many tales of "good folk" under hills and in deep wilderness point towards a dim cultural memory of ancient religious practices rather than spirits and gods. With fairie "maidens" such as the Banshee actually pointing towards priestesses of ancient agricultural cults. The mythical proclivity for stealing human children may in-fact point towards the tendency towards human sacrifice practiced by these ancient Sun King religions.
I should note here that all cultures have blood sacrifice ceremonies integrated in their history and philosophy (including Christianity).
Another thing to note concerning Fairies and Nature Spirits is that they are never depicted as terribly "good" in ancient tales, though they sometimes are helpful. Such beings are, by their very nature; fickle, amoral, and very, very strange. A mortal having dealings with such beings almost always runs afoul of the strange and seemingly arbitrary "rules" of the encounter. Terms such as "The Good Folk" point more towards a desperate attempt at appeasing the fickle and often cruel gods of the old world rather than a definition of their habits.
Still, the poems and songs relating towards fairie-kind, and the ancient gods are some of the most beautiful that I have ever heard or read. One, telling the tale of an ancient battle between the gods Amathaon ab Don, and Arawn and King of Annwn (Underworld), of which follows:
"Sure-hoofed is my steed impelled by the spur;
The high sprigs of alder are on thy shield;
Bran art thou called, of the glittering branches."
"Sure-hoofed is my steed in the day of battle:
The high sprigs of alder are on thy hand:
Bran by the branch thou bearest
Has Amathaon the good prevailed."
There will be more postings on these elusive and intriguing creatures soon (along with accompanying artwork). The piece depicted above will be developed and posted here as well.
Also, writer Daniel Hood and I will be working on future stories together, so stay tuned!