Ginaz
Dune notes that House Ginaz are "one-time allies of Duke Leto Atreides" and are "defeated in the War of Assassins with Grumman." Duncan Idaho is noted to be a Swordmaster of the Ginaz, which leads to his body later being sold to the Tleilaxu as "a master swordsman, an adept of the Ginaz School."
The Legends of Dune prequel trilogy by Brian Herbert and Kevin J. Anderson establishes that the planet Ginaz is oceanic with multiple, small tropical archipelagos that constitute its only surface land on which all the major population centers are situated. During the Butlerian Jihad, Ginaz mercenaries are renowned for their skill against Omnius. In the Brian Herbert/Kevin J. Anderson prequel series Prelude to Dune, House Moritani of Grumman attacks Ginaz after some of their students are sent home in disgrace from the Swordmaster School.
Read more about this topic: List Of Dune Planets