Vivian is a former member of the Shadow Sirens, but after her sisters pestered and made fun of her for years, she left the group and set a new course to rid herself of the "bad guy" role and take on Doopliss, the tyrannus prankster of the Twilight Town who's been fooling the civilians for what seemed like months. After figuring out his name, she got pretty far in the battle, but after a spell to revoke her voice, she was defeated.
Outside of battle, she's a shy individual. Mostly spends time in the dark as opposed to the day, or in the shadows.. literally.
FUN FACTS
Very bright lights can hurt Vivian, like it does with Boos, or Mario whilst his identity was stolen.
She's usually the best in a game of Hide & Seek.
She used to be a part of a group, but after constant harassment, villainy and other situations, she left the group.
She was the only other person to know Doopliss' name prior to telling Mario.