Mary is a supporting character in The Healer Who Was Banished From His Party, Is, in Fact, the Strongest. She is the owner and operator of a tavern in the dungeon city of Matatt, where she lives with her young daughter, Sheila. Her establishment serves as a lodging and dining place for adventurers, including the protagonist Raust and his partner Narsena, who become regular guests.

Mary is portrayed as a warm, hardworking, and practical woman. She runs her tavern single-handedly, demonstrating resilience and a strong sense of responsibility as a single mother. Her interactions with the main characters are consistently kind and supportive; she provides them with a safe and welcoming place to stay without judgment, even when Raust is widely regarded as an incompetent healer. She does not involve herself directly in the party's adventures but offers a stable home base and occasional advice or encouragement.

Her primary motivation revolves around caring for her daughter and maintaining the livelihood of her tavern. She has no notable combat or magical abilities; her role is strictly that of a civilian innkeeper. Throughout the story, Mary remains a steady, background presence who contributes a sense of normalcy and community to the setting. She does not undergo significant character development, as her function is to provide hospitality and a touch of everyday life amid the larger fantasy narrative. Her key relationship is with her daughter Sheila, and through her tavern, she indirectly supports Raust and Narsena’s journey.