The Silent Brothers are male Shadowhunters with superior powers. They serve several purposes for the Nephilim. To strengthen their minds, they have taken upon themselves the most powerful of runes known to Shadowhunters, which others of their kind never normally encounter, granting them access to the strange magic in the deeper parts of the Gray Book, and are thus mostly hidden and kept secret from others. They are feared among the Nephilim. They reside in the City of Bones.
The Silent Brothers have jurisdiction over the dead of the Nephilim, specifically those entombed in the Silent City. They are also sometimes responsible for holding criminals in their City's prison cells. They also serve as healers of the Nephilim.
They are the keepers and protectors of the Soul-Sword, which is hung in a chamber in the City of Bones. The judge who wields the Sword and hands it down to the deponent in trials is usually a Silent Brother. They possess the ability to recover memories, in a painful process that involves carving the truth from one's mind with the Sword.
- Telepathy: The Silent Brothers communicate with others through their mind.
- Special runes: While the Silent Brothers once possessed normal Shadowhunter Marks, they are able to draw more powerful runes on themselves.
- Memory access: Silent Brothers are capable of accessing the deeper recesses of a person's mind that they reach even otherwise blocked memories.
To strengthen their minds, the Silent Brothers possess unique runes, some of which mutilate their appearance. Their eyes and mouth are stitched shut.