A feather so black

"In a kingdom where magic has been lost, Fia is a rare changeling, left behind by the wicked Fair Folk when they stole the High Queen's daughter and retreated behind the locked gates of Tair na naOg. Most despise Fia's fae blood. But the queen raises heras a daughter and trains her to be a spy. Meanwhile, the real princess Eala is bound to Tair na naOg, cursed to become a swan by day and only returning to her true form at night. When a hidden gat...