Illyasviel von Einzbern is a fictional character from the Japanese visual novel and anime series "Fate/stay night." She is one of the central characters in the series and plays a significant role in its various storylines. Illyasviel, often referred to as "Illya," is a young girl with long silver hair and striking red eyes. She is portrayed as being innocent-looking and possessing a childlike demeanor, but beneath her exterior lies a complex and multifaceted character.