Tamir Triad Tome 3
The Oracle's Queen

For fear of an ancient prophecy, King Erius had his femle relatives assassinated. But his sister he spared, and the identity of her daughter was concealed at birth by dark magic. Now aged fifteen, Prince Tobin has been revealed as Princess Tamir, the true heir to the throne. Tamir's demonic twin brother, who was killed that she might be saved, still haunts her, but now that the spell that disguised her has been broken, he is no longer under Tamir's control...
and he is bent on vengeance for the sins committed against him. Meanwhile Erius's son Korin has claimed the throne and declared Tamir a traitor. But as the country slides into civil war the people begin to acclaim her as their saviour; for only she can save Skala from the disastrous rule of Kings...