Burning tower - Larry Niven

The people of Tep's Town are desperate. Monstrous invaders have emerged from the desert, and people are being slaughtered. Danger on the roads means no trade. No trade means that Tep's Town itself will die.

The fire god Yangin-Atep has retreated into myth, leaving the town's residents unprotected for the first time in its history - and they now face an army of fearsome birds with blades for wings, consumed by an inexorable lust for blood. Lord Sandry and his beloved, Burning Tower, must travel far beyond the walls of their home to discover the origin of these terror birds. They enter a world where magic is still strong - and someone or something has been waiting to destroy them ...