The Reaper Leviathan possesses a long, slim, muscular body with four caudal fins and two pectoral fins. It also has two dorsal fins running along the length of its entire body, and two ventral fins taking a small portion of its belly. Most of its fins, along with its back, are red in color. The fins and other red areas of the body possess slight bioluminescence. The Reaper Leviathan emits loud, echoing roars audible from great distances. It will circle its prey before attacking.