Perfect Dark Gaia

"When the beast is complete, its dark arms shall encompass the planet, ushering in the end of times. The world, in death, will fall into a deep sleep in waiting for the time of rebirth to come."

- Gaia Manuscripts, 4:28, Sonic Unleashed

Perfect Dark Gaia (パーフェクトダークガイア) is the true form of Dark Gaia and is the final boss of Sonic Unleashed. Every time Dark Gaia reaches the peak of its maturity, the beast assumes this grotesque form, which is composed of its premature form combined with extra body parts. As such, this form is the representation of the beast's true nature as a deity of darkness when it is ready to destroy the world.

Dark Gaia assumed this form during its battle with Sonic the Hedgehog and the Gaia Colossus when it reached full maturity during the course of the battle, but was eventually defeated by the combined forces of Super Sonic and the Gaia Colossus.

Appearance
Basically, Perfect Dark Gaia is identical to its immature Dark Gaia form, except that it now has gained extra features. Once matured, it grows four extra, identical arms, giving it a total of six arms. Its large mouth, which makes up most of its head, has been opened, revealing seven green eyes; three smaller eyes in each side and one large, central eye where its (former) visual mouth once was. It also gains two more tongues, which hangs out from each side of its central eye, similar to a dog's tongue.

Its seven tentacles move down from its spine to below the magma that it resides in. Their ends also gain more shape as well, resembling a serpent head with a small mohawk, and each with one green eye in their mouth.

History
Perfect Dark Gaia has been the true form of Dark Gaia ever since the creature's birth in the beginning of time. Since the beginning of its conflict with Light Gaia, Dark Gaia would assume this form when it had reached full maturity within the Earth's core and then rise from it to destroy the world, but would then be defeated by Light Gaia and resealed back in the core. In the following battle, Dark Gaia would lose this form and return to sleep inside the Earth's core to gather up enough strength to become Perfect Dark Gaia again.

In the beginning of Sonic Unleashed , Dark Gaia was interrupted in this process due to Dr. Eggman's awakening it prematurely with his Chaos Energy Cannon, resulting in Dark Gaia breaking apart and had to be reassembled. When Sonic and Chip's battle with Dr. Eggman's Egg Dragoon led them to Dark Gaia's location, Dark Gaia reabsorbed the final fragment of its power from Sonic's Werehog form, and it became physically complete, but it was not until after the initial battle with Sonic and the Gaia Colossus (Chip's transformation) that it fully regained its lost powers and at last became Perfect Dark Gaia.

Finally having become complete, Perfect Dark Gaia was now ready to cast the Earth into darkness and destroy the planet, but Sonic used the Chaos Emeralds to transform into Super Sonic and engaged Perfect Dark Gaia alongside the Gaia Colossus. At the end of the battle, Perfect Dark Gaia was defeated and fell into the Earth's core, where it once again returned to sleep while its dark energy that had been covering the Earth dissipated.

Powers and Abilities
Perfect Dark Gaia possesses the same powers as its premature form, such as firing energy beams, being able to pick up molten magma and control dark energies. However, due to having reached full maturity, it is now able to use its powers in a more refined and focused way.

In this form, Perfect Dark Gaia has enough physical strength to tear apart and effectively shattering an entire planet. It can as well manipulate its energies to form a hyper-energy shield around itself with its snake-like tentacles that not even Super Sonic can break through, with the only way to bring the shield down being to destroy its tentacles. It can also launch purple orbs at the size of Sonic in certain formations, as well as pick up and throw large blocks of magma with levitation, rather than using its hands and can launch its energy beams at a much faster rate. Also, it does not lose focus on charging these beams when it is attacked, unlike its earlier form.

As Perfect Dark Gaia, its weak points remains its various green eyes, like its earlier form, which are the primary targets of Super Sonic during his battle with it.

Wii/PS2 Version
The battle is essentially battling Alf-Layla-wa-Layla from Sonic and the Secret Rings, with Perfect Dark Gaia attacks, using the claws and energy blasts. As usual, Super Sonic needs to gather rings or he dies. The object of the battle is to gather rings and use them to perform the Super Sonic Boost and damage Perfect Dark Gaia's eyes one by one. However, each eye is defended by a number of floating rocks. When five eyes have been defeated, some rocks start moving in straight lines. The energy blasts can be deflected by pressing at the right time. Doing so will stun Perfect Dark Gaia, allowing you to collect more rings. The middle eye is the last one to destroy but it is always closed. It only opens if all six other eyes are damaged. After defeating the middle eye (with exclusively moving rocks defending it) the level ends and the final cutscenes/credits play (if you are beating him for the first time.) Otherwise, after the ranking screen, you are instantly whisked back to the level select screen.

The time needed to S-Rank Dark Gaia/Perfect Dark Gaia is 7:30, total. Anything less gives a C-rank.

Xbox 360/PS3 Version
This battle is much more complex than the other version. This version doesn't tell you much of the rules. Unlike other final boss battles in the Sonic series, Super Sonic is given a life gauge instead of a ring counter, which is increased when gathering rings and depletes when Super Sonic is hit by floating rocks or Perfect Dark Gaia's attacks. If Super Sonic's life gauge is emptied, the player will lose a life. In this fight, the player primarily controls Super Sonic, while playing as the Gaia Colossus during one quick-time event.

In the beginning of the fight, Perfect Dark Gaia sets up an enormous shield that Super Sonic can't break. Super Sonic and Chip (in his Gaia Colossus form) begin by advancing toward Perfect Dark Gaia, dodging the rocks and energy orbs. It is also important for the player to gather up as many rings as possible with the Super Sonic Boost to boost Sonic's life gauge, as there will be no other rings available after reaching Perfect Dark Gaia. After dodging the rocks, Super Sonic and the Gaia Colossus will reach the borders of the shield. Chip goes through the shield and distracts Perfect Dark Gaia, while Super Sonic goes and destroys the source of the power for the shield, which appear in the form of serpent heads that extend outside the force field. These serpent heads can be destroyed by making Super Sonic boost into them repeatedly, but the player must watch out for nearby rocks, which will cause the player to take damage if he/she don't avoid them. Chip has a life gauge as well, so the player must destroy the shield before Chip's life gauge is gone or he/she lose a life. Sometimes, Chip goes down and Perfect Dark Gaia starts to attack Super Sonic through the force field while the player tries to destroy the shield. It mainly attacks by shooting a large laser or calling several large rocks from the magma and throwing them at Super Sonic. Chip will eventually rise at some point and will try to distract Perfect Dark Gaia again, allowing the player to focus on destroying the shield again.

Once the shield is down, Perfect Dark Gaia grabs Chip with its six arms and starts to fire its laser to destroy Chip. Super Sonic goes out to save Chip by boosting into all six arms, which is done in gameplay by completing a quick-time event (in the order of, , , , , /, , , , , ), where Super Sonic has to land one hit on each of Dark Gaia's arms. After that, Chip is freed and leaves Perfect Dark Gaia in agony, but it still had enough energy to shoot its laser at Chip. Chip takes heavy damage from the laser, but withstands and manages to negate it (by pressing / sixty times within ten seconds). Once Chip negates it, he punches and directly hits Perfect Dark Gaia. Super Sonic then comes and finishes off Perfect Dark Gaia by flying through its middle eye. The level immediately ends after that.

Trivia

 * Perfect Dark Gaia is one of the two characters with the "perfect" prefix in their names, the other being Perfect Chaos. Both of these characters are final bosses.
 * In Sonic Colors, at the beginning of Act 6 of Asteroid Coaster, it looks like the roller coaster is coming out of a rock or planet that is shaped like Perfect Dark Gaia's head.
 * At the beginning of the Xbox 360/PS3 version, the fight against Perfect Dark Gaia is similar to Sonic & Knuckles' Doomsday Zone (Avoiding asteroids and collecting rings). However in this game, crushing to asteroid takes a small part of Super Sonic's energy bar, while in Sonic & Knuckles, it only stuns him for a few seconds.
 * Perfect Dark Gaia bears a striking similarity to the God of Darkness from The Chronicles of Inotia: Children of Carnia. Both have a similar physical appearance, both draw strength from negativity and Chaos in humanity, and both seek to destroy the world.
 * The lava during the boss fight is noticeably brighter in-game, while in the cutscenes it seems to be darker and gives off less light.