Cattleya is ranked No. 3 in Thanatos. She is the first woman in the history of Numbers. Until recently, she was manipulating Araragi to try to kill Mizuto. During that time, she was referred to as Edelweiss.
As Edelweiss, she wore a maid outfit and round large glasses, and she also did not speak very much. As Cattleya, she no longer has the glasses and wears a veil with Thanatos' symbol.
She uses a wide range of weapons, including a sniper rifle, knives, and many more. She was also the one who killed the Number 4, Sakura.
She uses strings to bind people and make them her "puppets". She tried this on Number 9, Anzu before which caused the latter to attack Toneriko. Anzu broke free from her grasp after.
She calls Ageha her "Master" though Ageha himself asked Cattleya to commit suicide since she attempted to kill Toneriko so many times. Ageha shut her up by saying "Yes, you were superior, but you weren't my favorite.". Catleya happily obliged and killed herself.