Ombria in Shadow — Patricia A. McKillip

When Ombria's prince, Royce Greve, breathes his last -- in palace rooms high above the city -- he leaves his young son and mistress at the mercy of his ancient and powerful great-aunt, Domina Pearl. Meanwhile, in a dreamlike underworld peopled by Ombria's ghosts, a sorceress weaves her spells and brews her potions, never revealing her real face -- or true heart. And somewhere in between, the struggle to rule the whole of Ombria -- both its light and shadows -- will rest in the hands of those whose fractured lives align like the lost pieces of a magical puzzle….