The Great Wise One is a patient teacher of any who make the effort to seek his guidance, trying to nudge his students to find the answers they seek on their own, rather than feed them the answers outright. The Great Wise One does not take sides in any dispute, choosing instead to take the side of all living creatures, and the Mother of Light that calls them her children.
~ in-game description

The Great Wise One is a being of myth said to older than time itself. After Horn releases the Chieftain of Cuthbert from his Pygon form, he advises Horn to go to the sea and seek him out. After Horn unlocks the Pygon Gate, he encounters the Pygon form of the Great Wise One, the Leviathan of Suddene. After he destroys its dark heart, the Great Wise One is returned to normal, and it turns out he is a talking whale. Though he is a whale, he still has great knowledge of the Pygon Curse and the world itself.