Gregar, known as Glaga (グレイガ Gureiga) in Japan, is a Cybeast from the Mega Man Battle Network series that was born through the accumulation of multiple bugs, the same method that created Gospel, explaining their similar appearances. However, the accumulation of bugs was natural in Gregar's case, as opposed to being man-made.
When Gregar was born, it attacked and destroyed the Net and everything in it. As a solution, scientists created Falzar to fight it. According to the games storyline, Falzar's involvement in battling Gregar made the Net's condition even worse. So one day while they were fighting, the NetNavis built a pit around them. This pit was known as the Underground, where they were trapped. Over the years, the two became dormant.
In the Cybeast Gregar version, 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. In the "Cybeast Falzar" version, nearly identical events happen, but with Falzar inside MegaMan rather than Gregar.
Gregar is later forced into a giant CopyBot and is deleted by MegaMan.
Gregar is, in the anime, very different from his game counterpart. He is originally from a world called Beyondard, which is a world where an alternate Lord Wily created a Dimensional Area Generator that exploded and caused a permanent merge between the cyberworld and real world. Gregar and his army of Zoanoroids are at war with Falzar and his own over the right to rule, and the Synchronizer, Trill. During the first episode of Beast, Gregar and Falzar do battle in both the real world and cyberworld, only to be stopped by both of MegaMan's base beast forms after fusing with the infant Trill. Near the end of Beast, Gregar defeats Falzar, to which Wily fuses the two together to create a Super Cybeast. This configuration then defeats the Cross Fusion Members in Lan's world only to be stopped by CF Beast MegaMan.
Gregar is a being that originated from bugs which were 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 it's just an illusion.
In volume 13 of the manga Gregar and Falzar fuse together and become the powerful Super Cybeast, 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.
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. Gregar actually possesses 2 hitboxes, its head and its torso; thus, area-hitting attacks are capable of inflicting double damage to it. Gregar sports 2500 HP in its normal version, 4000 HP in its SP version, and 5000 HP in its RV version.
- Airshoes: Gregar can stand over holes.
- Rock Fall: 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.
- Lightning Breath: Gregar fires its Elec Breath, hitting the front of MegaMan's area and his current row.
- Burning Breath: Gregar fires its Heat Breath, covering the panel immediately in front of it and the back two columns of MegaMan's area.
- Gatling Tail: 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.
- Beast Out Impact: 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.
- Beast Pressure: 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.
The Gregar Battle Chip is exclusive to the Japanese version.
- In the MegaMan NT Warrior manga, the Viz English translation, his name was misspelled as Graygar in one panel.