Thief of Llarn - Gardner F. Fox

Sword and planet by Mr. Fox, creator of Kothar.

"Among the ruins of fabulous cities and fallen empires, Alan Morgan becomes a prime piece in a time-spanning game of planetary chess. His prize--the incredible jewel of Zaxeron, held in an impenetrable light shaft guarded by all-destroying fires.

And always at stake--the life of Tuarra, crown princess of Kharthol and wife of Alan Morgan. For this was more than a mere game of living chess. It was war for a world!"

In great condition. Cover by Gray Morrow