|“||The Riders of Mannan have done the bidding of the Unseelie King for a thousand years. In that time many have fallen to our blades, and we have spared none for any reason, not for age or weakness or infirmity of body. We will not spare you now.||”|
|“||We seek. And we find. We are the searchers. We have been under the waves to search and above them. We have been in Faerie, and in the realms of the damned, and on battlefields and in the dark of night and the bright of day. In all our lives there has only been one thing we have sought and not found.||”|
The Riders were ruthless with their targets. The Riders were often tasked to kill a target or find an object or person, during which they would not hesitate to kill anyone who gets in their way or anyone who could help them achieve their goal. They are expert hunters, their skills on par with, if not greater than, the Wild Hunt's.
The Riders were initially made up of seven members: Karn, Etarlam, Eochaid, Delan, Airmed, Fal, and Ethna—Ethna being the only female member of the group. The Riders were siblings, or at least consider themselves as such, and were fiercely loyal to one another. They rode steeds that coalesce from the air, and the angelic weapons of the Nephilim were ineffective against them. Also despite being faeries, they were wild magic and were capable of lying.
They were much taller and larger than other faeries and all had bronze skin and hair, donning half masks of gleaming metal. Each was armed with a massive longsword, among other weapons, including a flail. The Riders wore armor without joints or rivets, simply smooth bronze that covered their whole body.
In 2012, the Riders were sent by the King to retrieve the Black Volume of the Dead. Because the King suspected that the Blackthorn family had the book or knew where it was, the Riders followed that lead and went after them. Because some were protected in the London Institute, they split up into two groups and went after two sets of Blackthorns who had been out and about in England: Karn, Etarlam, and Eochaid went after Ty and Livvy Blackthorn and Kit Herondale in London, while Delan, Ethna, Airmed, and Fal went after Emma Carstairs and Julian Blackthorn in Cornwall.
In London, Eochaid recognized Kit as Rosemary's child. The Riders pursuing him and the twins were intercepted by Gwyn ap Nudd and Diana Wrayburn, however, and were forced to leave. Meanwhile in Cornwall, the Riders fought Emma and Julian until Emma killed Fal with her sword Cortana. This shocked the Riders, as no one had ever been able to kill any of them, making Emma the first to kill a Rider.
All six remaining Riders later went to the London Institute, using a human child to lure them out. Emma was the first to come out and confront them, and the others followed shortly after. When they were just about to overpower them, Annabel Blackthorn and Magnus Bane arrived and drove them away. Annabel made them leave with a threat to the King, telling them that she knew his name, granting her power over him.
The Riders returned to the Unseelie; they guarded the tower and the King's new prized possession, Ash Morgenstern. The Riders caught Clary Fairchild and Jace Herondale investigating in the Unseelie Lands and took them prisoner. During the coup d'état staged by Adaon and others, the Riders tried, and failed, to defend the King.
The Riders were present at the staged parley between Arawn's successor Oban and the Cohort at the Imperishable Fields. They went after Emma and Kit, and when they told him that they'd killed his mother, Kit uncontrollably unleashed magic. Though the Riders tried to flee, Kit made their horses disappear, and the Riders fell onto the battlefield. They fought against the Shadowhunters, dedicated to seeing through the job their late King had given them, and were temporarily dispatched by Hypatia Vex. When Emma and Julian's parabatai curse was activated during the battle and turned them into true Nephilim, Emma called upon the Riders. The Riders came and went against them despite standing no chance and were all killed.
- The Riders were often mistaken for the Wild Hunt because of their flying horses.
- Seraph blades exploded when they came in contact with the Riders.