Namon was a character in a Vori mind-altering simulation that was used to brainwash Chakotay. They wanted to recruit him into their armed forces and make him hate the Kradin, who were their enemies.
Namon befriended Chakotay, but was killed in an ambush by Kradin soldiers. This helped condition Chakotay to hate the Kradin. (VOY: "Nemesis")