Hammerfall by C.J. Cherryh

Since he was eight Marak did his best to conceal the visions he saw and ignore the voices he heard beacuse he knew that either condition is considered asa sign of madeness. those wjho are deemed mad are turned over to the Ila. Until he turned thirty, Marak successfull hid his delicate situation. He enjoyed the war against the Ila, trying to break into the great city where she lived in splendid security. Marak confesses his illness and his fatherdisowns him, giving him over to hte soldiersfor disposl to Ila.
After travelling across a large dessert, Marak meets the five century old Ila. Everyone who is dubbed mad hear voices telling them to go east. Ila wants him to do just that bot report to her what he finds. After a long arduos trek, Marak reaches a towe where he meete Ian and Lutz, Ila's peers, claiming the world is coming to an end. If he is to survive he must return to this tower with Ila and as many people as will go with them.