The Four Diamonds (1995)

Young Christopher Millard fantasizes about being a squire of the Round Table and studies the stars. But when his difficulty breathing turns out to be caused by a tumor, his fantasies turn into a means to battle the disease. Chemotherapy eats his summer and instead of writing the standard "What I did during my summer vacation", his teacher lets him write a fictional story, and Chris makes characters from the people around him. As Chris battles with doctor, treatments, and the illness, Squire Millard goes on a quest against an evil sorceress to gain the four diamonds of Courage, Wisdom, Honesty, and Strength: qualities that Chris himself attains as his health fails.