Karrst was a human male who had the ability to use the Force. Working with his brother, Filin, Karrst killed at least one hundred people. Ren, the leader of the dark side organization known as the Knights of Ren, sought out Karrst to recruit him into their ranks. When Ren required Karrst to kill his brother in order to join them, Filin instead killed Karrst, attempting to join in his place. However, Filin was unable to use the Force, and was killed by Ren.