Zar'roc was the Rider's sword of the fallen Dragon Rider Morzan and had been once wielded by Eragon. Brom kept it following Morzan's death and later gave it to Eragon. Murtagh, Morzan's son and Eragon's half-brother, then reclaimed it from Eragon, since it was rightfully his by birth, at the Second Battle of the Burning Plains. The name "Zar'roc" meant "misery" in the Ancient Language. The name "misery" complemented the sword's actions, for Zar'roc was known for its destruction of many Dragons and their Riders.
Zar'roc's pommel was tear-drop shaped, set with a ruby the size of a small egg. The hilt was wrapped with silver wire. The blade itself was blood red, while its sheath was the color of red wine. Both the blade and sheath were marked with a "strange-looking symbol" that was etched in black. This symbol was a glyph in the Liduen Kvaedhí which presumably translated as "misery" to match the Ancient Language name of Zar'roc. Zar'roc was crafted by Rhunön, the elven smith who made all the Riders' swords. Though Zar'roc was a weapon that brought much pain and suffering, it was also a thing of great beauty. Zar'roc was 3 1/2 feet long. Eragon also thought the hilt should have been longer, so he could fight better two-handedly. This sword was a one-handed sword because Morzan liked to be able to fight with one hand and use Magic with the other.
Zar'roc was originally created by an Elf named Rhunön, the smith of the Dragon Riders. It was forged with a special metal found by Rhunön called brightsteel. Zar'roc was one of the last swords Rhunön forged before the Fall of the Dragon Riders and probably the most famous, along with Brom's sword, Undbitr. The sword originally belonged to Morzan, but was taken by Brom, another Rider, after his death. Before Morzan's death, Zar'roc was feared by many as his ultimate weapon. It symbolized agony and betrayal, as Morzan had killed many Riders with Zar'roc. When Brom first gave the sword to Eragon, it felt like it was made for him, but he told Rhunön that he would like her to make a sword that was different then Zar'roc, implying that some parts of his first sword were not satisfactory. The Dwarves had not trusted Eragon when he turned up on their doorstep carrying the sword of a traitor, yet Hrothgar believed its luck had changed. He was right as Eragon used the blade to defeat his and the dwarves' enemies. Brom gave the sword to Eragon, although he refrained from telling him the blade's history, in belief Eragon would be disgusted and horrified by what had been done by the blade. The history of Zar'roc was eventually revealed to Eragon by Murtagh while they were traveling to the Varden. Eragon used Zar'roc to defeat Durza, a Shade of immense power, in the Battle under Farthen Dûr.
After defeating Eragon at the Second Battle of the Burning Plains, Murtagh claimed Zar'roc as his own, declaring that Morzan's sword should have gone to him, the older son of Morzan, and not Eragon, the younger (which later proved untrue as Brom was revealed to be Eragon's real father). "Zar'roc" in the Ancient Language means "misery" and Murtagh found this name fitting. When Eragon faced Murtagh again, Murtagh managed to wound Eragon with Zar'roc and Eragon felt a strange sadness of being wounded by the weapon he originally wielded.
When Murtagh and Thorn went to battle Oromis and Glaedr, Murtagh used Zar'roc against Naegling. When Galbatorix took command of Murtagh's body, he used Zar'roc to kill Oromis, finally destroying the Riders of old.
Zar'roc was still in Murtagh's possession when he and Thorn went into self exile.
- Several inconsistencies exist between the movie Eragon and the book. Zar'roc has a ruby embedded into the hilt, however in the Eragon film it instead is a sapphire. Morzan's insignia appears on neither the sheath nor the blade in the movie. The sheath is also black rather than wine-red, like in the book as well as the guard of the sword which is gold in the book and silver in the movie. What's more is that the handle of the sword is leather-black, not silver-wrapped like in the book.
- In the movie, Brom used Zar'roc for the majority of the film, while in the book, he gave it to Eragon as soon as they fled Carvahall.
- When Brom gave Zar'roc to Eragon, Eragon asked what its name meant. Brom stated that he did not know, but whether this was actually true or not is uncertain: though most likely a lie, based on Brom's extensive knowledge of the Ancient Language and the fact that he and Morzan were once close friends.
- Eldest, p.652