Born in the town of Bree, Wrnach abandoned his family for unknown reasons and went on to do criminal activites where he earned his place in the Ruffians. During the time when the War of the Ring began, Wrnach and the Ruffians pledged their allegiance to Saruman the Wise, a former member of the White Council who betrayed the free peoples of Middle-Earth and joined the Dark Lord Sauron's cause in ruling all of Arda. Before Saruman orchestrated his plan to imprison Gandalf, Wrnach was in Isengard in the time and became spy-master to Saruman. His job was to coordinate the actions of Saruman's loyal agents, assassins, envoys, messengers, and spies.
Eventually, he had rarely left Isengard and had traveled to Bree where he spent the entire night smoking in the Prancing Pony which was owned by Barliman Butterbur, a member of the Butterbur Family. He would notice four Hobbits who came all the way from the Shire. Despite his title of Spy-Master, Wrnach did little spying and would witness Frodo Baggins disappering when the One Ring slipped into his finger and vanished in front of everyone. Much to his surprise and hear the name Baggins, Wrnach would send his report to his master on what had happened. Saving himself from most circumstances, Wrnach returned to Isengard and served as a clerk where spent days in coordinating Saruman’s reconnaissance activities.
Working from a small chamber in the fifth portion of the ring-wall, Wrnach wrote reports that consolidated scraps of information from the spies, messengers, envoys, and message-birds from afar. Wrnach also listened carefully to the words of the informants who maintained discipline in Isengard, and used them to weed out any betrayal from within. However, he would witness the arrival of an army of Ents and Huorns led by Treebeard, who had come all the way from Fangorn Forest to extract their revenge for killing or cutting down as many trees to be used for constructing armor and weapons for Saruman's army. He managed to escape Isengard just as one of the Ents wrecked the dam and the whole ring of Isengard was flooded. Wrnach was considered one of the few survivors that fled Isengard's destruction.
- The Lord of the Rings: The Fellowship of the Ring (First appearance)