The leanan sidhe (literally “fairy-lover”) exemplifies the dangers inherent in faerie gifts: that they are rarely gifts. There is always a price, an exchange. The leanan sidhe also personifies the costs artists pay to follow their muse—sometimes sacrificing fortunes, health, and even their lives in the process. And the leanan sidhe illustrates how narrow the line is between fey and other monster types with their almost vampiric feeding habits.
Speaking of which, where a leanan sidhe is found is likely a symptom of how aggressively she feeds on life energy. A leanan sidhe who is a reclusive nature spirit behaves like a dryad, gathering around her the pleasing and talented thralls who happen to come her way. Her tokens may even be bargaining chips to convince these servants to protect sites of natural beauty. Other leanan sidhe act more like vampires, heading into urban societies—high, bohemian, or both—to from cliques, salons, or schools around themselves from which to draw ample talent for entertainment and feeding.
In a low-magic or historical campaign, facing a mythic creature like a leanan sidhe might also be a good way to introduce high-level/more magical play. A Celtic or Anglo-Saxon party might have had a grand old time with clan politics, hewing goblins, and fighting Romans, but when they run afoul of the sidhe suddenly their world is changed forever. And of course on some worlds a leanan sidhe might be the Leanan Sidhe, a singular entity in the vein of Jim Butcher’s Dresden Files…in which case her class levels and mythic ranks might go even higher.
To learn a masterpiece, a bard and his friends must track down a musician currently in the hands of a leanan sidhe. Not only will they have to convince the musician to give up the fey’s tokens before her life draining kills him, but they will also have to defeat her “lapdogs”—former slaves she had infected with lycanthropy once she was done with them.
Disguised as a college chambermaid, a leanan sidhe has managed to bring the Chair of Transmutation under her sway. Seemingly rejuvenated by her possets and tender ministrations, the man has become addicted to her various blessings and the great flexibility they give him in spell selection and recovery. Meanwhile, she quietly stokes his rivalry with the Chair of Abjuration, coaxing him into experiments that undermine the wards protecting the college.
A leanan sidhe becomes enchanted with the masses sung at a temple famous for its chanters. Her zeal for the music is such that she attempts to convert to worship of the faith, but she soon becomes frustrated by the dogged silence of human deities. The mercurial fey decides that the priests have been mocking her all along, and by the time adventurers arrive at the scene the rectory is rife with factions, accusations, and bloodshed, with the leanan sidhe egging on her various charmed and blessed servants into greater and greater acts of debauchery.
—Pathfinder Bestiary 4 180
Intellectually I’ve always known I’d get a bigger response if I included pictures (something I’ve hesitated to do because of rights/permission issues). But still…wow.