Shaes are among the coolest-looking new outsiders to arrive in the Bestiary 3, and they bring new life to the sparsely populated Plane of Shadow. With masterwork falchions, a tidy list of shadow-related abilities, and heat-sapping strikes, they should make a nice challenge for low-level parties (with added class and prestige levels keeping them relevant in high-level play).
They’ll also certainly be a role-playing challenge even if no swords are drawn—their superior attitudes and too-casual treatment of their human harems (and fetchling get) should aggravate and even outrage morally-minded PCs. While some may be found out in the wilderness of the Plane of Shadow, honing their bodies and minds in the pursuit of perfection, most—already convinced they are perfect—will congregate in the shadow cities that mirror the Material Plane, enjoying the attention and special treatment they feel is their due.
And what is under those masks…?
Adventurers seek the expertise of a plane-hopping hunter at his exclusive club, only to discover that the lounge sports some grisly trophies: the masks and falchions of slain shaes. Coincidentally, a strike team of shae shadowdancers and assassins arrives just after the party does, seeking revenge. Now the adventurers are trapped in the club under assault from both sides—the club members believe they are accomplices, and the shaes assume everyone in the building is culpable.
A shae arrives at the doors of a monastery with a challenge—that his ascendancy can beat any representatives the masters send to face them. The shaes seek to prove that their pursuit of self-mastery outperforms the narrow lawful path of a monk.
A duchess comes begging adventurers for help. Her 16-year-old daughter has run off with a shae dancing master. Finding the pair will take them to the Plane of Shadow and the dark mirror image of their own city. There they will find numerous other women the chauvinistic shae has spirited away, now eager to return home, and a fetchling who claims to be the 16-year-old, abducted and transformed long ago…but surely that is impossible…?
—Pathfinder Bestiary 3 242