The Sentinel is a complete story by Nigel Kitching, Ferran Rodriguez and Ellie de Ville. In Kintobor's Laboratory, Sonic has been informed by the Kintobor Computer that something weird has surfaced in the Aquatic Ruin Zone. Since all of his friends are busy, Sonic goes alone. He spots the "king-size Badnik" but first has to contend with smaller Whisps. He soon frees them, but is sent plunging into the ocean by an arrow trap. A pillar falls on him, rendering him unable to reach the air bubbles. However, he's rescued by the giant Sentinel, who was left behind by the Zone's former inhabitants. With nobody left to protect, the Sentinel quickly breaks into pieces and ends his life.