Ancient beasts are devil beasts said to live for thousands of years. They are different from the Devil Beast Kings, and many of them lie dormant in the depths of the earth, the oceans or the clouds. Common wisdom says that even if you find one, you must never approach it.
A gigantic multi-eyed aquatic ancient beast sleeps at the bottom of the Mineshaft of Elbe, with the Waterfall Slicer resting on its head. It was probably awakened by mining and is the reason the hero Kodwar died there. It cannot leave the water. Alicia later faces an image of it inside Milea’s Mirror Prison and cuts it apart.