Gregar

Gregar, known as Glaga (グレイガ) in Japan, is a Cybeast who was born of the same method that created Gospel, which is why they are so similar in appearance. However, the accumulation of bugs was natural in Gregar's case and not man-made.

MegaMan Battle Network 6
When Gregar was born, it attacked and destroyed the Net and everything in it. As a solution, scientists created Falzar to fight it. One day while they were fighting, the Navis built a pit around them. This pit was known as the Underground, where they were trapped. Over the years, the two became dormant.

Gregar, along with Falzar, were released by CircusMan.EXE in an attempt to capture them for Dr. Wily, and depending on the games version, would go rampant or get captured by CircusMan. MegaMan.EXE tried to stop him by forcibly downloading it. Even though Lan and Yuichiro Hikari try to stop him, he still downloads Gregar, and falls unconscious from the strain. Afterwards, Lan collects Healing Water and uses it on MegaMan to weaken the Cybeast. However, Gregar rejects the water, and takes control of MegaMan. He then attacks HeatMan.EXE and nearly deletes him. Again, MegaMan falls unconscious, and Yuichiro states that Gregar may take control of MegaMan the next time he fights, and so, may have to be deleted. Later, after working on him, MegaMan gains the ability of Beast Out and soon afterwards, deletes CircusMan with it. However, he later loses control again, becoming GBeast.

Gregar is later forced into a giant CopyBot and is deleted.

Attacks
Gregar is the final boss of the Gregar version of Battle Network 6, and its side of the field cannot be Area-stolen. If the player happens to lose Area through use of Colour Point or Double Point, Gregar will not move forward, making Gregar's fire breath attack unavoidable. It also appears to be capable of standing over holes. Gregar sports 2500 HP in its normal version, 4000 HP in its SP version, and 5000 HP in its RV version.
 * Beast Pressure: Gregar jumps up and two rocks rain down on MegaMan's area when it lands. After repeating this for 2-3 times, it will follow up with one of the following.
 * Mane Lightning: Gregar fires its Elec Breath, hitting the front of MegaMan's area and his current row.
 * Gregar Breath: Gregar fires its Heat Breath, covering the panel immediately in front of it and the back two columns of MegaMan's area.
 * Tail Cannon: Gregar readies its tail and fires it up and down the player's column. In the SP version, this attack also tracks MegaMan's current column as it is in use.
 * Big Claw: Gregar disappears. Then, a 2x3 area just in front of MegaMan's back column lights up. Its claws will slash that area, while its head will rush down the row. It destroys a loaded chip for every hit. In the SP version this attack will destroy all chips and Program Advances loaded if it connects at least once.
 * Mega Beast Tackle: Gregar roars, then charges down its row. Rocks will then constantly fall down randomly on the player's area, with one always tracking MegaMan's position.

Anime
(in need of information)

Manga
In the MegaMan NT Warrior manga, Gregar is a being originate from bugs that was sealed in the Underground. MegaMan accidentally awakened Gregar during his battle against Nebula Grey when he obtained the ability to Beast Out. Gregar then started rampaging all over the Underground. Several NetNavis were summoned to the Underground and fought each other in order to choose the strongest Navi that can use the "Ultimate Program" from Iris in order to destroy the two Cyber Beasts. MegaMan, however, triggered his Beast Out form again to fight against Colonel.EXE and CircusMan.EXE, and Gregar felt a part of his power was inside MegaMan, suddenly appearing and roaring. His roars, however, ended up the battle as CircusMan was deleted and Colonel left suddenly, and MegaMan can controls his new Beast Out form then. Gregar also disappeared, through it was shown that his power is beyond imagination, even if just as an illusion.

In volume 13 of the manga Gregar and Falzar fuse together and become the powerful Cybeast Grezar, which is able to appear in the real world, absorbing it into the cyberspace. 60% of Earth is absorbed by it when MegaMan and Bass reach its core and destroys it, making everything return to normal.

Trivia

 * In the MegaMan NT Warrior manga, the Viz English translation, his name was misspelled as Graygar in one panel.