Lambert was a demon with the ability to look human.
Lambert was seemingly a regular at the Pandemonium Club in New York. One evening, he came to the club and was recognized and simply let in by the bouncer. Before entering the club, he overheard a girl asking about the hidden Enkeli rune on the club's sign. She was dismissed by the bouncer and the girl's friend, as both mundanes could not see the sign. He let the bouncer allow the two into the club for it.
Once inside, Lambert watched the girl, Clary, for a while before noticing Isabelle. Lambert approached her, but when Lambert began moving away bits of her dress and exposing more of her skin, he noticed her runes and realized that she was a Shadowhunter too late as her brothers, Jace and Alec had arrived. Together, the three killed him in the middle of the club, amidst oblivious mundanes—save for Clary, who screamed upon witnessing his death.
- The whole encounter involving the demon is significantly different in the book and the film.
- While the demon was never named in the book and the film, he was credited as Lambert. According to his portrayer Chad, the name was a reference to Adam Lambert, from whom his look was inspired.