As the gang arrive at the location of the final two sealed Numbers, above a stormy ocean, Rio suddenly starts hearing a voice in her head and is drawn towards the ocean; and she dives into it. Shark, Yuma and Astral dive in after her and wind up in a mysterious world underneath the sea, following Rio's footprints to a strange labyrinth, where Shark becomes separated from the others. Arriving at a temple in the center of the labyrinth, Shark finds Rio, who has been possessed by the Number's guardian, Abyss, and is challenged to a duel. Sharks summons out Black Ray Lancer while Abyss summons out Gorgonic Guardian, using its powers to destroy Black Ray Lancer. When Abyss projects a strange light, Shark sees a vision in which he and Rio were rulers of an ancient civilization, which was attacked by Vector. As Shark's life points are knocked down to 200, Dumon appears before Yuma and Astral. (thetvdb.com)