Lapis Mercurius Freya is a character from the visual novel and anime series Princess Holiday. She is a mysterious young woman who lives by a lake and is known locally as the Witch beside the Lake. She regularly visits the Korogaru Ringotei pub as a customer. Her appearance is that of a teenage girl with long blonde hair and purple eyes, typically dressed in a mantle and a pointed hat, often carrying a staff. She is sometimes seen flying on a broom.

Her background is largely unknown to those around her, and her true identity remains a secret. Despite her youthful appearance, she possesses an extensive knowledge of many subjects and seems to see through situations and people with ease. She is able to use advanced magic that is unfamiliar to others in the setting, wielding it effortlessly. This combination of deep knowledge and powerful magic gives her an air of wisdom and detachment.

In terms of personality, Lapis is calm, perceptive, and often speaks in a manner that suggests she understands more than she lets on. However, she knows very little about romantic love or emotional matters, which sets her apart from the other characters. Her motivations are not explicitly driven by personal desire; rather, she appears to observe and interact with the world around her out of curiosity or a sense of duty tied to her hidden role.

Her role in the story is that of one of the main heroines, a regular presence at the pub who occasionally assists the protagonist, Cliff Cloud, and the other characters with her knowledge and magic. She maintains a somewhat distant relationship with most people, though she is a familiar figure in the community. Through the course of the narrative, she may develop a deeper understanding of human emotions, particularly love, as she becomes more involved with the others. Her notable abilities include her powerful and unusual magical skills, her extensive knowledge of history and the world, and her ability to fly on a broom.