The Appendix IV: The Almanak of en-Ashraf (Selected Excepts of the Noble Houses) in Dune states:
COUNT GLOSSU RABBAN (10,132--10,193) Glossu Rabban, Count of Lankiveil, was the eldest nephew of Vladimir Harkonnen. Glossu Rabban and Feyd-Rautha Rabban (who took the name Harkonnen when chosen for the Siridar-Baron's household) were legal sons of the Siridar Baron's youngest demibrother, Abulurd. Abulurd renounced the Harkonnen name and all rights to the title when given the subdistrict governorship of Rabban-Lankiveil. Rabban was a distaff name.
In the novel, Glossu Rabban is the older nephew of Baron Vladimir Harkonnen. He is as cruel and sadistic as his uncle, but lacks his intelligence. The Baron tasks Rabban to rule the planet Arrakis for a time in the most brutal way possible, so that when his favored nephew Feyd-Rautha takes over, Feyd will be welcomed as a hero by the populace. After the Baron seizes the planet back from Atreides control, Rabban tells his uncle that the Harkonnens have woefully underestimated both the numbers and threat of the Fremen population there. Known as "the Beast Rabban" on Arrakis for his aggression and cruelty, his Fremen nickname is "Mudir Nahya", which translates as "Demon Ruler" or "King Cobra". Rabban is killed by the Fremen and the people of Arakeen when Paul "Muad'Dib" Atreides retakes Arrakis using Fremen forces.
Rabban was played by Paul L. Smith in Dune (1984) and László I. Kish in the Dune miniseries (2000). In the 2000 miniseries, the character is killed in the same manner as in the novel. In the 1984 film version, Rabban is beheaded by the Sardaukar when the Emperor Shaddam decides to eliminate the population of the planet.