Instructions
Destroy the eyes of the Dark Star so that he is unable to see you attack his legs. If you try to attack his legs before his eyes, he will retract his legs and hide them. To defend yourself against the Dark Star's moves, attack the Energy Orbs with your hammer, jump over the wave attack and jump when the Dark Star chases you.
Attack the Dark Star's legs after his eyes are gone. Once you destroy his legs, he will enter into his second form.
Dodge the purple beam attack by jumping and grabbing onto the Dark Star.
Jump to dodge the chain attack, and then deflect it with your hammer once he throws it at you to damage him. Continue to attack the Dark Star until you defeat him. Do it quickly, or else he will revive himself into his first form.