Berial attacks by firing beams from its weak point, the eye and creates option-like eyes that also fires beams. When you defeat Berial, the eye remains. It grows into Zelos Force. Zelos will fire two volleys of beams before self-destructing. Lots of Gradius players hate that especially when they've got hit a bunch of times, but a good strategy to avoid that is as soon as Zelos fires his beams push pause to see where they're going then unpause when you see them.