Karsh is a noncannon Wraith, created specifically for EA's The Lord of the Rings: The Battle for Middle-earth II: The Rise of the Witch King. He is played by Jason Connery.
Originally, Karsh was an Arnorian general named Carthedan. But after causing trouble to the Witch-King of Angmar, he decided to turn him into an undedead wraith. Since then, Karsh is devoted to the Iron Crown of Angmar. Karsh is playabe as a hero in the Angmar faction.