Compared to the Gool, Navalon has a much more bulbous shape. The top features a tower that serves as a lookout tower while a smaller ship is held within the Navalon. A pair of wings extend from the sides of the ship with two thrusters underneath.
The Navalon is armed with several weapons like missiles and beams. It is also able to stir up a tornado. It is able to fly through the thrusters on the wings. Like several other fortresses it holds a battalion of Mechanical Beasts.
After Sirene escapes her confinement during a battle with three Mechanical Beasts, Dr. Hell follows her in the Navalon to the Himalayas. Once Dr. Hell takes control of the Demons through microchips, he observes the events that transpire from the fortress. Later as the Mazinger Z attacked the fortress during an attack, more Mechanical Beasts were sent to attack it, but Devilman intervened. As Devilman is captured, the Navalon is present as the demons torture him. Suddenly the Mazinger appears flying through the Jet Scrander, using its Breast Fire to destroy the Fortress. Dr. Hell and Baron Ashura managed to escape on the smaller ship before anyone noticed.