Appears in Stage 5 (The Third Moon), Scene 5.
Fulmenorca is one of Meio's three lifeforms created during his battle with Hiryu. This flying lifeform is a transparent being in the shape of a small whale or similar sea-based animal with three glowing rings inside its "body" and a red core within its "head". The Fulmenorca has the power to generate lightning bolts from its core.
When summoned, Fulmenorca appears at one extreme of the area and flies or "swims" back and forth constantly. When close to Hiryu, it then stops and charges up a lightning strike aimed at him, then resumes its movement. Fulmenorca only moves across the platform height where he's summoned until disappearing or defeated, so if it appears on the upper platforms it will not move into the lower ones and vice-versa, making it easy to avoid.
When Caduceus is summmoned, two Fulmenorca stand in the middle section of its "arms", connecting Graveleo and Ardoravis together. They also grant Caduceus the ability to shoot stronger and far-reaching lightning from them, aimed directly at Hiryu.