Spudio the 22nd hails from the annihilated second dimension, destroyed by the Sphinxes. Dispatched as a messenger by Oedipus, this living meteorite summons four high school students and their teacher into a dimensional classroom. His core mission: facilitate battles against the soul-consuming Sphinx family, whose dimensional ascension threatens all existence.

Initially manifesting as an inert rock in the human world, he activates to transport the group into a two-dimensional realm. During the puzzle-solving confrontations, he serves strictly as announcer and guide. After initial victories prompt the group to attempt his destruction, their teacher, Mr. Momoya, secretly rescues and preserves him. This hidden survival proves pivotal when Mr. Momoya later reactivates Spudio to orchestrate a deliberate sacrifice to the Sphinxes.

Spudio's background reveals deeper ties to the human world: guided to the protagonists by Shiro Oide, Mr. Momoya's deceased friend later revealed as Oedipus reincarnated. This linkage underscores his role as an instrument of Oedipus's plans. Despite his mechanical obedience, his actions enable the students to uncover truths about Mr. Momoya's past and Shiro's identity. In the final arc, Spudio assists the students in returning to the dimensional classroom for the climactic battle against the Black Sphinx, directly facilitating their rescue of Mr. Momoya.

His existence intertwines with the core conflict of dimensional collapse and the Sphinxes' soul-consuming ascension, positioning him as a catalyst for the protagonists' challenges and their development.