Dark Druid Elf Tiefling

This is an elf druid that has been granted demonic powers by dark forces, which has altered his body in diabolical ways. In the rpg I ran, he was a villain that had taught one of the group's major villains how to do bad things to the elven people who kicked her out (the homeland of a number of the players and npcs). The group defeated and imprisoned the student, and later fought the master (after gaining enough levels to be able to deal with him).