There are two stages where you will encounter Amorbis. In one stage, Amorbis will leap into the air and back into the ground, where its impact will damage you if you are close to it. Use your radar more often to see where Amorbis is located. Stay inside the Light Crystals to avoid being damaged by the atmosphere. As it leaps up into the air, shoot it with the Power Beam, Light Beam, or missiles. After several hits, it will be time for stage two. On stage two, it will stay at the center of the arena and will use its physical attacks. Be careful, as Amorbis will also disable the Light Crystals. Move on to the next one if that happens. It will also shoot multiple blue energy beams on the ground. The best way to dodge these is to morph into a ball inside the Light Crystals and hover around the energy beams. Blast Amorbis down with the Power Beam, Light Beam, or missiles. Its head will explode and it will try to suck you in. Quickly form into a ball and let it suck you in, then drop some bombs inside it. The battle repeats both stages again, but with two, then three worms and it gets tougher. Once Amorbis is defeated, the Dark Suit is yours.
In his first form, Amorbis will be jumping out of the ground then going back in. He is vulnerable when he is in the air. Shoot him with Charge Beam so you can conserve your missiles for the second form. When you break off its shell, it will attach to the sphere in the center of the arena and go into its second form. It will then have an outer plate on its head, which you can break with a couple of missiles. When it looses its plate, it will try to suck you up. At that time, go into morphball and lay a bomb in its mouth. Repeat this for two worms, then three. Also, when Amorbis has two or three heads, it is able to use a laser attack. Finally, Amorbis has the ability to disable the Light Crystals in the arena. You will have to move to the next crystal every so often.