After completing the first of the "rotating-box-shoots-you-through-a-tunnel" puzzles, you will find a room with the "corrupted forma" (don't ask) in it. Go to the bottom of the room and activate (press A) the pedestal that is NOT red. This frees the corrupted forma so it can attack you (the ingrate!). When you "shoot" a bomb at it, it shoots it straight back at you. You have to have one of these red, reflected bombs hit each of the three red Pedestals. With each pedestal taken out, the ingrate looses one of its tentacles. Good luck! ...actually, it's not as bad as it sounds. WAIT!
Don't leave the room without picking up the item on the floor to unlock this: