Leysritt is a homunculus created by the Einzbern family to serve as a maid much like Sella. Despite her appearance, she is only about two years old.
Regardless of her thin ego, she developed a sense of reason due to her alignment with Illya. As a result, Leysritt often says what she thinks without any consideration and this gets her often into a verbal conflict with Sella.
She and Illya are actually very close friends and should Illya die, Leysritt would die as well. In contrast to Sella, she possesses a casual personality but has difficulty expressing her emotions and comes across as robotic at times. However, she appears to enjoy teasing Sella and also takes a liking to Shirou because his presence makes Illya happy.