Riesbyfe Stridberg appears in Carnival Phantasm as an adult woman with neck-length white hair and purple eyes. No details about her background, personality, specific role, development, dialogue, actions, interactions, or narrative arcs within Carnival Phantasm are provided. She is identified as a minor or background character in the series, which primarily focuses on characters from Fate/stay night and Tsukihime.

Information from other Type-Moon media documents her role as a Shield Knight of the Church who sacrificed her life protecting Sion Eltnam Atlasia from the Night of Wallachia. This event led to her subsequent existence as a TATARI materialization. She is associated with the Conceptual Weapon "Gamaliel". These specific narratives from other works are not connected to her portrayal in Carnival Phantasm in the available sources.