Angels are winged celestial beings which have fought against the demon legion for eons. According to legend, it is an angel, specifically Angel Raziel, who created the Nephilim with the Mortal Cup and his blood.
All Shadowhunters have some level of angel blood in their veins, specifically that of their creator, Raziel. However, an exceptional amount of pure angel blood—Ithuriel's, as a result of experiments by Valentine Morgenstern—runs in the veins of a number of Shadowhunters, giving varied results, namely:
- Clary Fairchild was unwittingly given an exceptional amount of angel blood, particularly Ithuriel's, while in her mother's womb by Valentine. This connection with Ithuriel allows her to see and draw old runes—those not documented in the Gray Book—sent to her through visions by the angel.
- Jace Herondale was also given Ithuriel's blood, also while in his mother's womb, as part of Valentine's experiments. It gave him innate strength and skill far superior than ordinary Nephilim, along with the ability to activate runes on his and others' skin without the need of a stele. It also makes his eyes glow gold when he uses his rune-activating ability. This excess angelic blood also turned the vampire Simon Lewis into a Daylighter and protected him from the effect of the Soul-Sword.
- Jocelyn Fray was given doses of angel blood by Valentine, unwittingly giving her daughter angel blood as well. She, like Clary, also received some ability to use runes unconventionally, though in a lesser degree compared to Clary's; for example, she and Clary were both able to place—and later withdraw—three-dimensional objects within an otherwise flat surface or material, such as on drawings or paintings, but she does not have access to other runes that Clary has.