The Crystal King - The Tanarian Chronicles, #2

Two prominent nations have locked horns on a collision course of destruction, a fight that will bring one side to its knees. Faced with overwhelming odds, the Tanarian nation flounders as the ravages of war extract a heavy toll, with the invader pushing ever deeper into their lands, their fate will surely soon be sealed. Yet they still have one advantage, Tamar the magician, the greatest mastermind of their time fights for their survival and his own.
He fights evil in his own uncompromising way and hopes to exploit a potential weakness in the massing forces they face. However, he can only work with the limited tools he has; a maverick warrior filled with his own agenda and fuelled with the lust for revenge, a misled thief, and a king who may yet turn against him. Only on Athene, a lady gifted with an immunity to magic, can he depend upon in this struggle - but perhaps he asks too much of her? Only through his manipulation, deception and an iron resolve have they any hope of survival.