Remilia resides in her mansion with her two servants, Sakuya and Hong Meiling, her friend Patchouli Knowledge, and her younger sister Flandre. Despite being approximately 500 years old, her personality is very childlike and selfish. As most vampires she has immense magical and physical powers, but is weak to direct sunlight. During the events of The Embodiment of Scarlet Devil she went as far as to release a red mist over Gensokyo, so she could walk outside and host parties during the day. After the incident was resolved, she was made to wear a parasol any time she wanted to come out during daytime.
Being a light eater, she only drinks a little bit of blood from her victims, leaving them more anemic and less dead than usual. In fact she spills more blood than she drinks, which gives her dress it's scarlet color. That in turn has led to her title, the Scarlet Devil.
She claims to be a descendant of Count Vlad Tepes Dracula, but that apparently is a complete and utter lie.