Evelyn was born to the Highsmith family in the 1930s. Due to the standing of her family and the time she lived in, she was raised with the disdainful views and attitude towards Downworlders. At some point in her life, Evelyn became the head of the London Institute.
In 2012, Evelyn housed the Blackthorn family in the Institute after an attack by Malcolm Fade on the Los Angeles Institute. She ignored them for the most part, having accepted them only because of her fondness for Arthur Blackthorn, a former resident of the Institute. The Blackthorns, in turn, kept her in the dark about their plans, and she showed no interest in involving herself. At times, when Evelyn wished to make an inappropriate side comment, she would pretend to be reacting to something spoken by the Institute's ghost, Jessamine Lovelace.
The arrival of Kieran, Magnus Bane, and his children, among them another warlock, the young Max, infuriated Evelyn. She tried and failed to have them kicked out. Evelyn eventually left the Institute, not wanting to be surrounded by Downworlders, and went to Sussex to visit the Blackthorns' aunt Marjorie, leaving Alec Lightwood temporarily in charge. She returned to the Institute shortly after so that Alec and his family could return to New York.
Evelyn is an imperious and old-fashioned woman who dislikes Downworlders and children.
Evelyn is a tall white-haired woman in her eighties who wears long 1940s-style dresses and carries a silver-headed walking stick.
- Nephilim physiology: Being Nephilim, Evelyn possesses a variety of enhanced physical and mental abilities granted to her by the angel blood of Raziel in her veins and also by the angelic Marks of the Gray Book. This includes enhanced strength, speed, agility, stamina, and coordination, which continue to improve over time and practice.
- The Sight: As a Shadowhunter, Evelyn is naturally and easily able to see through most magical illusions and layers of glamour over reality.
- Runic magic: Due to the angel blood in their veins, all Shadowhunters are able to apply runes on their skin without any real danger. These Marks, in turn, give varied effects that serve to benefit the wearer.
- Use of heavenly weapons: As a Shadowhunter, Evelyn is also able to perform tasks unique to their species, such as the ability to use and call on the power of angels for their seraph blades, as well as to handle any heavenly weapons or objects with effect, which would normally not work for other species. In particular, these are tools made of adamas and forged by Iron Sisters.
- Walking stick: Evelyn possesses a silver-headed walking stick that she uses due to her old age.