Queen of Air and Darkness

Queen of Air and Darkness is a powerful eldritch archfey who ruled over the Unseelie Court. The Queen of Air and Darkness has no physical form; her presence is merely felt in the Unseelie Court. If magic is used to see her, however, she appears as a beautiful but terrible female faerie with angular features, bone-white skin, all-black eyes, and long black hair. The Unseelie Court are the foes of the Seelie Court. She is opposed by the elven deities of Seldarine, namely Corellon Larethian, Erevan Ilesere, Rillifane Rallathil, Sehanine Moonbow, Solonor Thelandira, and Angharradh. To them, she personifies the corruption that could grow even in those of fey lineage. Auril the Frostmaiden is believed to be synonymous with the Queen of Air and Darkness by some communities of fey, such as those of the Shiverpine Forest in the Deep Wilds.
She is served by unseelie fey, including brambles, quicklings, and spriggans. She is also known to have a fondness for yeth hounds and hell hounds. The glouras, fey beings of the Underdark, had ties to the Queen of Air and Darkness and the Unseelie Court.
Once, the Queen of Air and Darkness was the sister of Queen Titania, ruler of the fey, in the land of Ladinion. But one day a group of dwarves, who had been mining in a mountain to the south, brought to the Seelie Court a great, ten-faceted black diamond they had found as a gift for the fey queen. However, Titania was away swimming that day so her sister accepted the gift. This diamond began to corrupt her, transforming her nature, and one day she took the diamond and other magical treasures and left in a chariot of smoke and fire that was said to have appeared out of the sky. Some time later the mountain that the dwarves were mining exploded, slaying the dwarves and causing sickening smoke to cover the land.
 The Black Diamond, sometimes called the Night Diamond, is an artifact of immense power and evil of unknown origin. It sits atop her throne in the Unseelie Court.
Encountering her on the material plane is a rare and often overlooked occurance, either in the way of a chilled winter breeze or an eerie whisper in the darkest of night.