Biolizard

The Biolizard (バイオリザード) (also known as The Prototype of The Ultimate Life Form) is a creature which appeared in Sonic Adventure 2 as the final boss. It appears as a giant lizard with a life support system on its back with tubes running down its neck to its head. The Biolizard is 85 meters (280 feet) long, 30 meters (100 feet) wide, 19.5 meters (64 feet) at the tallest point on it's back, and weighs 87.5 tons. After the final version of the Ultimate Life Form was created, the Biolizard was to be encapsulated but never was.

Sonic Adventure 2
The Biolizard was an early version of Project Shadow, a government project run by Professor Gerald Robotnik that was intended to create an "Ultimate Life Form" as a first step towards humanity discovering the secret of immortality. This creature is an ultimate immortal, or so the scientists thought. Due to the experiments weakening the Biolizard, it later needed a life support system. While the Biolizard was successful in the way that it could regenerate, restore itself, and self-reproduce, it was also unruly and dangerous. It was closed down when Gerald, with the aid of the alien Black Doom, produced a more advanced being: Shadow the Hedgehog.

When GUN came to Space Colony ARK in order to put a stop to Gerald Robotniks plans, they found the Biolizard and shut it down. It didn't go without a fight, however, and it destroyed almost the entire group of GUN soldiers.

thumb|276px|left|Shadow vs BiolizardThe Biolizard remained in suspended animation aboard the ARK until the present day, when Doctor Eggman placed the seven Chaos Emeralds into the Eclipse Cannon. This initiated a program created by Gerald Robotnik, which used the power of the Chaos Emeralds to send the ARK into a collision course with the Earth. Eggman joined forces with Sonic and friends to prevent this doomsday scenario, and they tried to pull the ARK into orbit again by using Knuckles' Master Emerald to deactivate the Chaos Emeralds.

However, when Sonic and Knuckles entered the cannon's core, the Biolizard awakened, determined to keep the ARK on its path to Earth. Later, Amy Rose convinced Shadow to help save the Earth (Shadow had a flashback about his best friend, Maria Robotnik, yet in Sonic X it was Chris Thorndyke who reminds Shadow of Maria instead of Amy.) Shadow fought and won against the giant reptile by damaging its life support system. The Biolizard then used Chaos Control to teleport outside of the ARK and fuse with the space colony itself, becoming The FinalHazard, the final boss of the game. It was fought by the combined power of Super Sonic and Super Shadow, who then used Chaos Control to place the ARK back into orbit. Both Shadow and the FinalHazard fall to their apparent deaths (though it is later revealed that Shadow survived).

Shadow the Hedgehog
The Biolizard was mentioned in Shadow the Hedgehog, but only in one of Shadow's flashbacks, when he remembers his apparent death after defeating it. The Biolizard was likely just an example of Gerald's work before Black Doom assisted him, and thus is of little interest to the Black Arms and wasn't stable because he didn't have Black Doom's DNA. However, it is noted that after Black Doom transforms into Devil Doom, he has an identical cry to that of Biolizard. Several other Black Arms have similar cries. Also, the Black Annelids, Black Worms, and larval black warriors ("Death Leeches"), have a skin texture very similar to the Biolizard's. This presents the possibility of the Biolizard actually being a Black Arms experiment, but it was simply unsuccessful, or not successful enough. As it turns out, Devil Doom and Biolizard's cry is just a reused version of Perfect Chaos' cry, and the Biolizard is just a lizard that was horribly mutated. The fact that it has the same skin color as the Black Arms is probably because Sega reused the skin color for the Black Arms, and therefore might be a coincidence.

Sonic X
The Biolizard's role in the anime Sonic X parallels the one it plays in Sonic Adventure 2. It appears in episode 38.

In the series, the creature is not specifically named as a prototype of Project Shadow. In the original Japanese version, Knuckles identified the Biolizard, but in the English dub, it was unnamed, and Knuckles instead simply stated that he wouldn't let the monster get the Master Emerald. When Professor Gerald's diary reveals what really happened on the ARK 50 years ago, a small green lizard was shown that could have been what the Biolizard looked like before its current state.

Abilities
The Biolizard fights by spitting dark energy balls, biting, or lashing its tail at Shadow. After chasing the hedgehog for some time, the lizard stops and seems to hyperventilate, which is Shadow's chance to grind up a green tube that connects the Biolizard's head to its life support system and attack it. After damaging the system a few times, the Biolizard creates dozens of pink egg-like orbs in the air, and fires them at Shadow. Shadow must then use homing attack on the orbs in order to get into the air and attack the life support system again. Finally, the Biolizard will somehow lift Shadow himself up into the air along with the orbs, and as such he must float towards the life support system while avoiding the orbs in order to defeat the Biolizard.

After transforming into FinalHazard, the Biolizard uses the power of the Chaos Emeralds to enhance itself while also gaining the ability to fire large pink energy beams from its broken life support system, and create similar orbs to the one before. Only the new ones are red and the FinalHazard creates hundreds of them to cover itself as a shield. It also fires them at Super Sonic and Super Shadow a few at a time. As his life support system has been demolished, the FinalHazard has grown large pink boils all over its body, and Super Sonic and Super Shadow must charge into these boils in order to harm it.

Theme songs

 * Biolizard: "Supporting Me" by Everett Bradley.
 * Finalhazard: "Live and Learn" by Crush 40. (Shared by SA2 as the Main Theme)

Trivia

 * According to Rouge's report in a cutscene in Sonic Adventure 2, Biolizard was made on January 27th at 12:30 a.m.Biolizard_file_2.png
 * According to Rouge the Bat's report in the official strategy guide from Sega, the pink-orb objects the Biolizard produces are produced through asexual reproduction, which means that there could have been more than one Biolizard, however this is unlikely. It is often assumed that the Biolizard, is in fact, female (due to the eggs), but this is unlikely because additionally, the Omochao that appears during the battle refers to the Biolizard as a "he," further adding to the confusion. However, Biolizard may produce asexually much like a gecko.
 * When Biolizard summons the pink spheres and later levitates Shadow, the roar used is the same roar used for Perfect Chaos in Sonic Adventure.
 * The Dreamcast version of Sonic Adventure 2 had glitches in the game that led to unavoidable deaths when fighting the Biolizard (such as landing in the water as opposed to on the platform).
 * When playing the Dragon Slayer mission in Sonic and the Black Knight, Sonic sometimes mentions the Biolizard. The Earth Dragon, in fact, may be the Arthurian version of the Biolizard due to being so similar in body type, having the same neck, and even a similar roar.
 * When the Biolizard becomes FinalHazard, he loses some limbs like a missing arm, which might have been caused from his fight with Shadow or when attaching himself to the Eclipse Cannon.
 * In Sonic X, the Biolizard appears to have back legs, while in Sonic Adventure 2, it has two flipper like appendages located in front of its tail.