High Sidhe
The High Sidhe are nigh-indistinguishable from humans, beautiful past mortal possibility, and hold the entirety of the Kingdom's nobility. They are what every lesser Faerie is told they may one day become, and the promise is the mechanism by which the whole society holds together.
Almost every High Sidhe carries an artifact of the "lesser" race they metamorphosed out of — a hint of scales at the wrist, a tuft of fur at the nape, an ear a shade too pointed. Concealing these from one's social peers is a lifelong occupation and the subject of an entire minor industry in the Ring.
Appearance
Tall, symmetrical, and unnervingly perfect, with wings larger and more ornate than any other race's, kept summoned at all times as a display of leisure — a Faerie who never needs to fly anywhere can afford to keep their wings out.
Attuned Magic
Arcane, which is to say all of them and none of them well. Where a lesser Faerie has one element and profound depth in it, a High Sidhe has a shallow command of many, and can do a little of everything a specialist would do better. The court holds this to be evidence of a higher and more complete nature. Every specialist race in the Kingdom privately holds the opposite.
Society
The Ring — a belt of noble estates encircling the Eternal City — is the most exquisite and most artificial landscape in the world, grown at ruinous expense in soil hauled in from the provinces. The houses compete relentlessly in beauty, in humanness, and in proximity to the Queen, whose own status is a matter of live theological dispute: whether she is a High Sidhe herself, or some yet-higher tier reserved for her alone.
Relations
Every race in the Kingdom answers to them, and no race is on equal terms with them. The Sylphs serve them most closely, the Leprechauns supply them, the Spriggans sell them things they cannot be seen buying, and the Kitsune bless them in careful language. Nothing about this arrangement is examined in public.