The War Lord by Barry Sadler (Casca Series, Book 3) from Books In Motion.com

Casca awoke from a drugged sleep and saw his spear thrust into the side of the man on the cross. His spear...lost when he was sent from Judea! It wasn't a vision--it was the beginning of a threat which would follow Casca through eternity, and cost him the use of his hand. As Doctor Goldman is soon to learn, it is just the beginning of an adventure which would take Casca behind the Great Wall of the Hidden Empire, China. He would rise to the position of War Lord, and heir to the throne, only to be buried alive at the whim of a frustrated royal concubine.