Gurney Halleck was a ruthless, noble, and romantic warrior of enormous talent. He was the most loyal of friends to those he loved, and to those he hated there were few enemies more terrifying. He was a talented minstrel who was skilled in the use of the baliset. His jawline bears a scar from an inkvine whip wound inflicted by Beast Rabban in the Harkonnen slave pits. In a fight against Gurney with sword or knife few opponents lasted more than a few seconds. Gurney was also skilled at various other weapons, and astonished Fremen later saw that he taught himself to ride sandworms as they did.
Gurney Halleck did not indulge in melange addiction or other methods to prolong human life. He had been a loyal friend to Duke Leto Atreides and his concubine Lady Jessica. Many years after the death of Duke Leto, Gurney Halleck became the lover of Lady Jessica, though the two of them kept their relationship out of the public eye so as to avoid scandal.
Paul Atreides, recalling a line of Islamic poetry quoted to him by the Reverend Mother Gaius Helen Mohiam after his test of the Gom Jabbar, named him 'Gurney the Valourous'. Siridar Duke Leto I commented that Paul named Gurney well. The poem's line is as follows :
There are four pillars which support the world...the wisdom of the wise, the justice of the great, the prayers of the righteous and the valor of the brave.
In Children of Dune, Gurney returns to Arrakis with Jessica from Caladan. He coordinates a purging of dissidents along with Stilgar, an operation that he kept secret. He goes to the sietch Jacurutu under what he believes are Jessica's orders to test that Leto II has not fallen to Abomination. When the Fremen Namri reveals that the testing was ordered by Alia, he kills the man and escapes, sending a message to Duncan Idaho to set off the course of events that will force Stilgar to act. He goes to Tuek's Sietch, where he takes temporary shelter with a new batch of smugglers before stealing an ornithopter. With it, he escapes to a rebel sietch, where Leto II and The Preacher arrive. Leto II takes him to Shuloch. After Leto II returns to Arrakeen and takes the throne, Gurney is assigned to Sietch Tabr as part of Stilgar's Council.
According to the prequels, Gurney Halleck was born on Giedi Prime, the homeworld of House Harkonnen. After an incident with the local militia and the murder of his sister, he escaped Giedi Prime and aligned himself with the rogue House Vernius. Eventually, after a string of conflicts and the death of Earl Dominic Vernius, Gurney Halleck arrived at the Atreides homeworld of Caladan seeking the exiled Prince Rhombur Vernius. After helping reclaim the planet Ix for House Vernius, Halleck served House Atreides, eventually becoming Paul Atreides' weapons teacher.
In Chapterhouse Dune it is revealed that the Tleilaxu Master Scytale possesses a hidden nullentropy capsule containing cells carefully and secretly collected by the Tleilaxu for millennia, including the cells of Paul Atreides, Duke Leto, Jessica, and Gurney. This establishes the potential for gholas to be created of these individuals in Hunters of Dune and Sandworms of Dune, the sequels to the original Frank Herbert series written by Brian Herbert and Kevin J Anderson.
In the PC CD-Rom game, Gurney would often accompany Paul Atreides and upon joining Paul would say "Ok Paul, I'm coming with you."