Jamis is a Fremen from Stilgar's sietch, Sietch Tabr.
Aggressive and quick to temper, Jamis remains unconvinced of Jessica's mystical powers and challenges her champion, Paul, to a duel to test their worth. Guess how that works out for him? Yep, Paul kills Jamis in battle and earns all of Jamis's possessions, securing his place among the Fremen.
Jamis acts as a foil for Stilgar. Both display the best features of the Fremen people, such as strength and skill in combat. But whereas Stilgar tempers his strength with intelligence and knowledge, Jamis gives in to his anger, resulting in "too much of violence in [him]" (33.28).