The Forsworn (Wyrdfell in the Ancient Language) were thirteen corrupt Dragon Riders with Galbatorix at their head. They spearheaded a rebellion "out of desire for power and revenge against perceived wrongs". This rebellion was later known as The Fall.
As of Inheritance, five of the thirteen original Forsworn have been named:
Morzan was the first of the Forsworn. It was he who left a gate unlocked in Ilirea (later named Urû'baen), enabling Galbatorix to steal Shruikan and slaughter the black dragon's rightful Dragon Rider. Eventually, twelve more dissolute Riders came to support Galbatorix's cause. With their help, Galbatorix defeated the armies of the elves and dwarves, and murdered Vrael, head of the Riders. Two other Dragon Riders of the Forsworn, Kialandí and Formora, were mentioned in Brisingr, although not much is known about them.
At some point Kialandí and Formora captured the elven Dragon Rider Oromis, and used a spell taught to Galbatorix by Durza's spirits. This spell isolated Oromis from the energy around him, effectively preventing his hold on magic. The spell was weakened by quick action on Oromis' part, but it stuck with him and prevented Oromis from gathering more than a small amount of energy at a time for the rest of his life. Oromis finally escaped from the Forsworn and went into hiding in Du Weldenvarden along with his dragon, Glaedr.
Eventually, the Forsworn died out due to in-fighting (they often vied among themselves for power and favor, something which Galbatorix encouraged, and would often support one of the Forsworn over another for his own amusement), suicide, overuse of magic, and the efforts of Brom and the Varden. Morzan and two other Forsworn were personally killed by Brom; five died as an indirect result of Brom's zeal.
Glaerun was the only member of the Forsworn to die in the fighting at Vroengard, killed in an explosion caused by another Rider, Thuviel, who had lost his Dragon to the Forsworn in the months previous to The Fall.
In Brisingr, it was revealed that after the dragons who were not part of the Forsworn learned that their kin had betrayed them, they combined their magic together and performed the Banishing of Names, the Du Namar Aurboda. If someone looks at the name of a dragon or remembers their name it is instantly forgotten.
The traitorous dragons lost everything that made them dragons. They became no more than beasts with magic they did not know how to use. Their Riders could only watch as they sunk even further into bestiality. Five of the Wyrdfell (elven name for the Forsworn) became insane.
The dragons spared Shruikan, because he was forced to serve Galbatorix, and Jarnunvösk, Galbatorix's first dragon because she had no part in this. Their descent into ignorance led to the popular misconception that dragons were little more than animals and transport for the Riders.
One hundred years later in a tragic irony, Murtagh followed his father's role as a servant of Galbatorix, however he was not considered one of the Forsworn.
The Forsworn may be compared to the Sith of Lucas' Star Wars trilogy and to the Nazgûl of Tolkien's Lord of the Rings and the Death Eaters of Rowling's Harry Potter series, in that they were corrupted by the promise of power. They are also similar to the Forsaken of the Wheel of Time. They could also be put on par with the Witchmen of the Reach or also known as Forsworn from the Elder Scrolls series, who want revenge on the Nords.
- The fact that there are thirteen Forsworn may be a nod towards the fact that thirteen is generally considered to be an unlucky number.