Perfect Dark Gaia

Perfect Dark Gaia (パーフェクトダークガイア) is the final boss of Sonic Unleashed. He has 7 eyes and 6 arms. His final eye seems to be inside his mouth. He also appears to have 2 tongues. However, he has three (a smaller tongue is inside his actual mouth, if you look closely while playing. Two are hanging out, while the smaller tongue is hidden.). This is the last and final battle of the game. Perfect Dark Gaia is the true form of Dark Gaia in which it is the complete monster of the hyper organism. This is the complete form because the immature form of Dark Gaia was due to Dr. Eggman's premature awakening to it. Once mature, green blood splats out to have its 7 eyes and 6 arms. Sonic then looks at Perfect Dark Gaia in determination and the emeralds come out of the Gaia Colossus and he's turned to Super Sonic to finish off Perfect Dark Gaia.The music for this stage is the instrumental form of Endless Possibility.

Battling it
There are two different versions of defeating Dark Gaia. The Wii/PS2 version and the Xbox360/PS3 version

Wii/PS2
The battle is pretty much like battling Alf-Layla-wa-Layla when 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 game is to pretty much gather rings, use them for the Super Sonic Boost and kill the eyes. (However, each eye is defended by a number of floating rocks. When 3 eyes have been defeated, some rocks start moving in straight lines.) The energy blasts can be deflected by pressing the x button 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 is always closed. It only opens if all six other eyes are destroyed. 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 screen.

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

Xbox360/PS3
This battle is much more complex than the other version. This version doesn't really tell you much of the rules. Super Sonic and Chip (in his Gaia Colossus form) advance toward Perfect Dark Gaia, dodging the rocks and getting rings to boost Sonic's life gauge. After dodging the rocks, Perfect Dark Gaia sets up an enormous shield that Super Sonic can't go through. Suddenly, Chip then goes through the shield and grabs Perfect Dark Gaia's attention while Super Sonic goes and destroys the source of the power for the shield, which appear in the form of serpent heads that extend from the shield and must be rammed repeatedly. Chip also has a life gauge too, so, you must destroy the shield before Chip's life gauge is gone. If Chip goes down, Perfect Dark Gaia starts to attack you while you try to destroy the shield. He 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 grab Perfect Dark Gaia's attention. Once the shield is down, Perfect Dark Gaia then grabs Chip with its six arms and starts to launch its laser to destroy Chip. Super Sonic then goes out to save Chip by destroying all six arms. After that, Chip is freed and leaves Perfect Dark Gaia in agony, but it had enough energy to shoot the laser and it shoots at Chip. Chip takes immediate impact from the laser but withstands and manages to negate it (by pressing 60 buttons in 10 seconds on the controller). Once Chip negates it, he takes a punch and directly hits Perfect Dark Gaia. Super Sonic then comes and finishes off Perfect Dark Gaia by going through the middle eye. The level immediately ends after that.

After the Battle
Once after you're ranked, it shows Perfect Dark Gaia being immediately slashed through by Super Sonic by the middle eye and returning into the Earth. Super Sonic is then returned back to normal and falls from exhaustion. Gaia Colossus catches Sonic before falling into the magma. Earth is then dissipated of Dark Gaia's energy.

Links

 * The battle against Perfect Gaia(Wii/PS2 version)
 * The battle against Perfect Gaia(PS3/360 version)

Trivia

 * Perfect Dark Gaia in one of the two characters with the "perfect" prefix in their names. The other is Perfect Chaos.
 * 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.