Pineapple on 07 January 2010
Are you talking about the boss inside the Leviathan itself, called "Helithos" or something?
If so, shoot at the core when he starts flying around, you've nearly killed him. He should now have exposed his core, and you can just hypermode and shoot him down.
He's the only boss I can think this could be. A name or location of the boss would help greatly.
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