The creator is the final boss in the game. He consists of 4 battles.
First Form: Statue
The Statue form involves the Creator sitting to the right of the screen. He has two attacks in this first stage of the form: energy darts and spawned enemies. With his left hand he reaches out to spawn enemies, either three red jellyfish or one blue nautalis. Each of these requires a full blast with Dual Form (Li). Use these enemies to charge up Dual Form and unlease its scream attack on the creator. When the Creator begins to laugh, he will reach up with his right hand and unleash a massive assault of reddish energy darts. Use shield to avoid taking damage.
Alternatively, you can continue shooting him with Dual Form and running tight loops above the Creator's head. There you will miss the majority of the energy darts and take minimal damage while continuing to dish it out. You can get by without using Dual Form. Eat a food that improves your energy form shots and keep firing at him. You can kill his spawned minions pretty quickly with improved shots and he can go down before using his energy darts a second time.
Even simpler is to use nature form and shoot a big thorn on the wall behind the creator so that it extends into his skull. That should deal enough damage to make him change form almost instantly.
After dealing enough damage to the Creator, he will become mobile, and he also consumes Li removing your ability to use Dual Form. His legs are traded out for some tentacles and he gains some more attacks: energy beam, poisonous shots, and hand grab. If he grabs you, spin to get free. The poison darts can be avoided easily enough, but be prepared to cure your poison should you get hit. The energy beam is the hardest to avoid since you'll most likely be away from the Creator when he initiates the attack. It does a good deal of damage (about 1/3 full health). You can avoid it by being below the Creator when the attack starts or above his head.
Second Form: Maze Bug
The Bug form begins with the Creator fleeing through a tunnel of spines and mouth traps; all of these are easy to avoid and don't necessarily require the Sun Form. The final part of the run ends in a small maze-like structure, which the Creator runs around in while in Bug form. It is pitch black here, so use the Sun Form to illuminate your path. In the lower-left corner of the room is a plant containing a Dumbo Ice Cream for boosting your Sun Form. When you get near the Creator, you can hear the music get louder. When you see him, change to Energy Form (or Beast Form if you have a means of shooting) and fire at him as he begins to attack you. When you get close, he will open his jaws and attack you. Shoot him as he does this, targeting the object inside the jaws. Then he will flee again after shooting him. He can flee directly into you, so make sure to be out of the way after you hit him. Do this five times and he will flee to the third form.
Third Form: Simon Says Energy Sphere
The third form starts off with him still in Bug form. Damage him twice and he will immediately change into the third form. In the room you will notice eight orbs of white (situated like your song notes). During this form he will sing out three tones, lighting up the white spheres in the proper sequence. From these spheres will shoot energy spheres. You destroy the spheres by singing the notes the sphere was created with after the sphere has formed. Doing this for all three spheres will damage the Creator. If you are hit by a sphere, you take a good amount of damage and cannot damage the Creator in return. If you get into the top left of the screen behind the hooked formation, you can avoid being hit by all the spheres and simply sing notes to get rid of the spheres without taking any damage. Destroy the trio of spheres five times to defeat this form.
Final Form: God
In this form he's huge. He has two stages in this form. The first stage involves him attacking with fast moving energy balls (which due to their speed also make wide turns and are easy to avoid as long as you're moving when they are first launched) and spawning mutants which have their own ranged attack. Both types of projectiles can provide a steady supply of health when absorbed using the spirit form. He will launch energy balls from his mouth and from his hand at the bottom of the area (take caution with this as you can't see both areas at the same time). He seems to rotate using his mouth and his hand to attack, and he also alternates between using his hand to launch energy balls and spawn a mutant.
During this part you have to go for his right eye. At first it is covered up; shoot it with something to break the cover. It then bulges out. Use Sun Form's sun burst to make the eye vulnerable. Shoot it when it is vulnerable. Keep this up until it turns dark. Then use bind song to pull the eye out. When you do this, it will break open his chest, releasing Li (giving you Dual Form again) and moving him to the second stage.
The second stage involves him using his hand to release energy balls and his chest to launch a powerful beam (removes 1/2 health without added defenses). The beam is easy to avoid as it only fires straight out and doesn't actually target you. The screen turns blue for a moment and his chest opens up to release the beam. His hand releases energy balls as well and these can be avoided easily. In fact, if you stay near his chest area where the beam comes out, the energy balls can be dodged and they will collide with his chest and end. You can practically get rid of all the energy balls this way. The two attacks alternate so you're not at risk of being shot by the beam while using the above tactic to avoid the energy balls.
Right before he fires a beam, you'll notice a face in the chest area. Shoot this with the Dual Form just as the chest opens (preferably while not in the path of the beam). You cannot shoot it while the beam is firing or after the beam is done firing. After the beam is gone, if you hit the face, three blue nautalis will spawn. Use these to power the Dual Form's scream attack. Use the scream attack on the Creator from just about anywhere as long as he is on the screen to damage him. Do this three times to end the battle and end the game. Sit back and enjoy the ending(s).