The sun sword, book 3 : The shining court
Michelle West1999

In the Essalieyan Empire, Jewel, of House Terafin, has been having visions which are about to send her into the heart of enemy territory with only her domicis Avander to watch her back. Behind her she leaves a House on the brink of a bloody dynastic war--a house to which she is the unoffical heir. Before her lies the Dominion, home to the clans which are the sworn enemies of all who dwell in the Empire. But far more deadly than the clans are those with whom they have formed an unholy alliance--the demons of the Shining court !