Patricia A. McKillip 
Ombria in Shadow [EPUB ebook] 

The Prince of Ombria is dying, and already his sinister great-aunt is plotting to seize power. The Black Pearl is feared throughout the land, and the city folk know her reign will be a terrible one. Only the prince’s son can stop her from seizing the throne but he’s just a boy — barely worth the trouble of doing away with.Ombria, it seems, is doomed. And yet, beneath the streets, in a buried world of shadows and ghosts, a mysterious sorceress is weaving new spells, watched over by a girl sculpted entirely from wax …