Diababa (giant looking plant) is the first fighting to get the first shadow piece. To defeat him, first you have to use your boomerang and r target a bug bomb then second-target the plant and Diababa should eat it. (do the same with the other one). After that Diababa should reveal its full self. Keep dodging whatever it is throwing at you, then the monkey should come and swing on a vine holding a bomb for you. R target the bomb then r target one of the smaller plants. Do the same with the other side again. Now all their is left is the big middle one. r target the bomb the monkey is holding onto and r target the big plant and it will eat it. The big plant should now fall. Run up to it and attack its eyeball. Then the process should start over again. Keep doing it over and over until it dies. (note) their are hearts by the left and right wall.