Kargan was the Klingon captain of the Pagh, who served alongside Riker during an officer exchange and nearly attacked the Enterprise.
Kargan commanded the Klingon ship Pagh when William Riker joined it as first officer under an exchange programme in A Matter of Honor. He was a harsh commander, and he was pleased when Riker proved himself by overpowering the ship's second officer, Klag.
When a microscopic organism began eating through the Pagh's hull, Kargan concluded that the Enterprise had attacked his ship with a new weapon and ordered his crew to strike back. Riker used a transponder to have Kargan beamed off the ship, took command himself and resolved the standoff with Picard. Christopher Collins played him.