Dark Helios is one of the final bosses of Darius Burst, reappearing again in Darius Burst: Another Chronicle. Dark Helios is one of the flagships of Belser, it's shape based on the oarfish. Designed for defensive purposes, Dark Helios has a segmented body, with each portion covered in a hard armor. Though the joints are much less armored, it is almost impossible to attack them due to Dark Helios's incredible speed.
Dark Helios was built over the Syvalion, an ancient dragon battleship created by an alien race, which had been used in the past to defend humans from these same aliens. How Belser actually obtained the Syvalion is a mystery.