Radnor is the Mentat for House Harkonnen in Dune II. He is described as being unstable, having a lust for power, and an ability to persuade. However, the Dune II manual also states that the extent to which Radnor is trusted is unknown.
Radnor reached his position by assassinating the last Harkonnen Mentat, Marko, who had been his teacher and guide, which, according to the Dune II manual, makes him a true Harkonnen. In Dune 2000, the Harkonnen Mentat is Hayt De Vries, but there was no mention of what happened to Radnor.
Radnor is a bald male, who appears to have a hunch.