Karl Tanner a.k.a Clubfoot Karl is a former criminal sent to the Night's Watch to guard the wall between the seven kingdoms and the mysterious and dangerous North. Karl eventually betrays his brothers and Lord Commander for food and shelter at Craster's place.
Karl serves as the main antagonist, along with Styr, in the Night's Watch story line in season 4 of the HBO fantasy drama Game of Thrones and the ASOIAF novels written by George R.R. Martin.