Im writing a trilogy that has my antagonist start as a hero along with my protagonist. My Protagonist is a human prince, an heir to the most powerful empire in my world. He wants to change how his people treat non-humans, especially the hostilities between his empire and the Dark Elves. My antagonist is a Dark Elf from a highly militaristic society. They respect deeds more than birthrights even if his father is the King. He's driven to do something worthy enough to be named his father's heir by a council of elders. The two characters have already met before ch.1 and are working together to find a bow that is said to be blessed by the gods. Im having trouble on how to make my Dark Elf antagonist go from at least tolerating the race of men to outright despising them enough to want to eradicate them so other races can prosper. Every idea I have ends up being very cliche. Ideas?