Fairies are halflings, like trolls, falloys, ogres and goblins, and unlike merrihews, sandestins, quists and darklings. Merrihews and sandestins both may manifest human semblance, but the occasion is one of caprice and always fugitive. Quists are always as they are, and darklings prefer only to hint of their presence.
Fairies, like the other halflings, are functionally hybrids, with varying proportions of earth-stuff. With the passage of time the proportions of earth-stuff increases, if only through the ingestion of air and water, though occasional coition of man and halfling hastens the process. As the halfling becomes 'heavy' with earth-stuff it converges towards humanity and loses some or all of its magic.
The 'heavy' fairy is abusively ejected from the shee as a boor and a lummox, to wander the countryside and eventually merge into the human community, where it lives disconsolately and only rarely exercises its fading magic. The offspring of these creatures are peculiarly sensitive to magic, and often become witches or wizards: so with all the magicians of the Elder Isles.
Slowly, slowly the halflings dwindle; the shees grow dark, and the halfling-stuff dissipates into the human race. Every person alive inherits more or less halfling-stuff from thousands of quiet infusions. In human inter-relationships the presence of this quality is a matter of general knowledge, but sensed subliminally and seldom accurately identified.
The fairy of the shee often seems childlike by reason of intemperate acts. His character varies of course from individual to individual, but is always capricious and often cruel. Similarly, the fairy's sympathies are quickly aroused, whereupon he becomes extravagantly generous. The fairy is inclined to be boastful; he is given to dramatic postures and quick sulks. He is sensitive in regard to his self-image and cannot tolerate ridicule, which prompts him to a prancing demonstrative fury. He admires beauty and also grotesque oddity in the same degree; to the fairy these are equivalent attributes.
The fairy is erotically unpredictable and often remarkably promiscuous. Charm, youth, beauty are not cogent considerations; above all the fairy craves novelty. His attachments are seldom lasting, in common with his moods. He quickly shifts from joy to woe; from wrath through hysteria to laughter, or any of a dozen other affections unknown to the more stolid human race.
Fairies love tricks. Woe to the giant or ogre the fairies decide to molest! They give him no peace; his own magic is of a gross sort, easily evaded. The fairies torment him with cruel glee until he hides in his den, or castle.
The King of the Fairies by Horslips.
Fairies are great musicians and use a hundred quaint instruments, some of which, like fiddles, bagpipes and flutes, have been adopted by men. Sometimes they play jigs and knockabouts to put wings on the heels; sometimes mournful tunes by moonlight, which once heard may never be forgotten. For processions and investitures the musicians play noble harmonies of great complexity, using themes beyond human understanding.
Fairies are jealous and impatient, and intolerant of intrusion. A boy or girl innocently trespassing upon a fairy meadow might be cruelly whipped with hazel twigs. On the other hand, if the fairies were somnolent the child might be ignored, or even showered with a rain of golden coins, since the fairies enjoy confounding men and women with sudden fortune, no less than with sudden disaster.
Source: Glossary 1, Lyonesse by Jack Vance. Illustration by Les Edwards.