Kathi is the name of a make-up in Kathakali. It literally means knife and is donned by valorous characters having good or evil traits. Some characters portrayed in this make-up are Duryodhana, Keechaka, Ravana and Narakasura.
Though there are two types of Kathi characters viz., Nedumkathi and Kurumkathi, the latter one is more popular. Shown in the video is Narakasura in Kalyanasougandhikam, a famous Kathakali play.
Kathakali make-up is classified into five types according to the nature of the character. They are Pacha (green), Kathi (knife), Kari (black), Thaadi (beard) and Minukku (radiant). Thaadi is further classified into three viz., Chuvanna Thaadi (red beard), Vella Thaadi (white beard) and Karutha Thaadi (black beard).