Egg Viper

The Egg Viper (エッグバイパー) is the last boss during Sonic's story in Sonic Adventure and Sonic Adventure DX: Director's Cut. It is a giant viper-based mech created and is piloted by Dr. Eggman.

Appearance
The Egg Viper is designed after a large flying viper (hence the name). It has two large red and grey spiked wheels on both side of the cockpit which the Egg Mobile can fit inside. The cockpit itself is round-shaped and is covered in thick red and grey armor with two fins on the bottom, yellow and black hazard strips horizontally along the middle, a single fin op top with a red and grey tube on each side, and a large laser cannon down the front which can slide back to reveal the pilot. On the cockpit's rear it has three large red and grey flaps with a long red and grey segmented tail in the middle which has spikes and green spots running down it.

History
After braving the Final Egg, Sonic made it to the center of the base where Dr. Eggman was waiting for their showdown. The Egg Viper then arrived and Sonic followed it to the battle arena inside the Final Egg's main tower by using Rocket. After defeating the Egg Viper, Sonic and Eggman escape before the Final Egg exploded.

Boss guide
The player faces off against the Egg Viper right after completing Final Egg as Sonic. The battle starts while Sonic is standing in front of Egg Viper on two platforms above a bottomless pit. Each side of the platforms have a small set of Rings to be collected. The Egg Viper uses different types of attacks according to its health bar: After Sonic has completely depleted the Egg Viper's health bar, the machine will convulse uncontrollably and will attempt a suicidal attack, in which the Egg Viper will ram into the platform Sonic is standing on. A quick Spin Dash or Homing Attack is required. If it succeeds, it kills Sonic alongside the machine and they both fall in the bottomless pit; this can be problematic if Eggman has destroyed many platforms during his attack due to Sonic missing his chances to attack Eggman. If only one platform remains by the time Eggman attempts the suicide assault, Sonic's doom is certain.
 * 1) The first attack pattern is firing four or five laser beams from its tail in a row. To avoid this attack, Sonic must keep moving in different directions to avoid being hit. Eggman then simply reveals himself, allowing the player land the Spin Jump on him.
 * 2) The Egg Viper starts to charge and shoot an electric ball as its second attack. During the charging process, the cockpit exposes itself on the machine, giving Sonic a chance for attacking him. To damage him, Sonic can Homing Attack into the nodes on the Egg Viper's tail which leads up to the cockpit.
 * 3) The third attack pattern is shooting a powerful laser with the machine's laser cannon. First, the Egg Viper takes an aim at Sonic before firing. After a short time of moving, the cannon is fired and a quick reaction helps Sonic avoid it.
 * 4) When the health bar reaches half, the Egg Viper flies over the platform where Sonic is standing and shoots laser beams at Sonic's position as Eggman's gloats at him.
 * 5) The common attack pattern during the last half of the machine's health bar is launching its razor discs. This can be used to damage the Egg Mobile too. To avoid this, Sonic must get as far away as he can or just jump when the disc comes close. Once the disc stops, he can jump on it to reach the Egg Viper's top and attack it with the Homing Attack or the Light Speed Attack.
 * 6) After destroying the platforms on the other side, the Egg Viper destroys a platform where Sonic is standing and shoots its razor discs again. This pattern is used until the health bar reaches zero. If Sonic keeps missing his chances to hit Eggman in this phase, he eventually runs out of platforms and falls to his death.

Sonic X
In the Sonic X anime, the Egg Viper was used by Dr. Eggman as his secret weapon against Sonic after many of his previous plans were ruined by him. Despite this, the vehicle's role and functionality were pretty much the same. After a close-knit battle, Sonic destroyed the Egg Viper.

Archie Comics
In the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics, the Egg Viper was one of the elements introduced to Mobius Prime after the second Genesis Wave rewrote reality. During Worlds Collide, Sonic mentioned the Egg Viper when he and Mega Man are talking about snake-based enemies.

In the altered reality created due to the improperly-reversed Super Genesis Wave, the Egg Viper was also included. Its background is the same as its game counterpart.

Trivia

 * Like Egg Hornet and Egg Walker, the Egg Viper is code named "EG3". This code name is displayed around the vehicle's gray and orange metallic parts.
 * The Egg Viper is similar to the Egg Wyvern. Both bosses are the same color, both are suspended above low ground, both battles have a part where you attack Dr. Eggman head on, and both bosses destroy platforms and decrease the amount of space you have to run on.
 * The Egg Viper's height is about 130 ft.
 * The Egg Viper has been the start point of the trend where final bosses are seen having the last sudden attack. Certain cases include Egg King's final strike in Sonic Rush, Ghost Titan's final laser attack in Sonic Rush Adventure, the Death Egg Robot's final attack in Sonic the Hedgehog 4: Episode I and Time Eater's giant flaming fireball in Sonic Generations.
 * This boss, as well as the Egg Walker boss, is infamous for Eggman's line: "Get a load of this!"
 * The Egg Viper has the most health out of every boss in Sonic Adventure, even having more health than the final boss, Perfect Chaos.