Background
The Telmarines are the human people descended from the men of Telmar who eventually invaded and ruled Narnia. By the time of Prince Caspian, they have suppressed much of the older Narnian world. Talking beasts, dwarfs, fauns, and other old creatures survive, but largely as stories, fears, or hunted remnants under Telmarine rule.
How the Race Functions in Narnia
Lewis uses the Telmarines as a conquering human culture that has forgotten both Narnia’s true history and its proper relation to the land. They are not evil simply by bloodline. In fact, Prince Caspian himself is Telmarine. The problem is political and spiritual: they rule as occupiers, and many of them have grown suspicious of the very world they displaced.