Devil

The term Devil (named after the biblical entity) is used for a recurring type of enemy encountered in several Mega Man series. Although several have appeared in the original series, other variants have popped up in future timelines as well.

Description
The first several "Devil" robots were created by Dr. Wily to serve as some of the last lines defense of his castles against Mega Man's advance. In future time periods however, more advanced models have shown up, beginning with the Shadow Devil in Mega Man X5. No matter the name, shape or color, they all share one thing in common: A singular red eye situated within a malleable body made out of an unknown substance, the eye itself generally being its weak point as the rest of the body is usually impervious to all attacks. Despite their apparent shapeshifting abilities, most have not shown a wide range of forms when in battle. Their main attack has often consisted of breaking themselves up into pieces that dart over from one side of the room to the other and then reconstituting from that spot. Other than their color however, what distinguishes them from each other is in the fashion in which they attack or their sturdiness.

Most of the "Devil" series robots have the distinction of showing weakness reactions towards Electric-type weapons. The Green Devil and Shadow Devil bosses from Mega Man 8 and Mega Man X5 also have an electric-based weakness: Thunder Claw and Tri-Thunder respectively.

Yellow Devil
In the first Mega Man game, the Yellow Devil's only attacks were shooting its mass as a series of projectiles that would dart over from one side of the room over to the other in a set pattern, as well as a small projectile fired from its eye while whole. However, it was weak against Elec Man's Thunder Beam.

In Mega Man Powered Up, the Yellow Devil broke up into a whirling torrent of spheres before flying over to the other side.

Despite its inability to defeat Mega Man, its effectiveness to wear him down has prompted Wily to revise the robot in Mega Man 3 to make it sturdier and impervious to its preceding weakness.

New Yellow Devil
A variant created by the supercomputer Ra Moon to combat against Mega Man in Super Adventure Rockman. Also the first variant not constructed by Wily himself. Unlike the previous and future iterations, the New Yellow Devil was considerably more mobile, if not, more agile as it tended to jump around several feet forward or back. Its attacks consisted of an eye blast, a trio of red energy shots and by pounding the ground with either or both its arms. While it had the ability to morph into a mobile puddle to guard against Mega Man's buster attacks, it did not display the traditional mass projectile attack. Despite its name, it was primarily black in color and featured arm and leg bands with ancient symbols lined across their surfaces along with a collar with a similar design, making its design more detailed than most other Devils. Due to its resemblance to creator Ra Moon, it has been dubbed by fans (and in the Archie Comics adaptation) the "Ra Devil".

Green Devil
First appears in Mega Man 8 in the third Wily Tower stage, and then as the first boss of Mega Man & Bass. Rather than being made out of a more solid substance, its main body is made out of something akin to gelatin and its eye is that of a normal color rather than the traditional red, although it was located in the very center of the body mass. The Mega Man & Bass version is much weaker, losing all its previous mobility and most attacks and sticking to only one side of the screen.

Dark Moon
A servant of Terra, leader of the Stardroids in Rockman World 5, sent to destroy Mega Man after four of his brethren had been felled in combat. He seems to be considerably larger than the other Devils up to this point as his vertical columns consisted of five blocks rather than the traditional four. While he shares the same mass projectile attacks as most other Devils, he bounces the top two down due to his sheer size.

Twin Devil
A more unique variation from Mega Man 9. Instead of a humanoid creature, the Twin Devil was in fact two identical shapeless models that worked in tandem. Possessing the ability of flight, they have much dominion of the air and they attack by switching places, shooting pieces of themselves to each other's relative location until they've completely reformed and can adjust their height afterwards.

Block Devil
Another strange variant, from Mega Man 10. Unlike the other models, as it indicates, is blocky in nature and its pieces can wedge themselves into the occupying room's gaps and it situates itself in the center rather than in a corner. When fully formed however, it fires plasma beams to attack.

Grey Devil
Much like the Green Devil from Mega Man & Bass, this model was mostly immobile and its attack consisted of sliding three balls of goo across the floor before sliding to the other side of the room. It is featured in

Shadow Devil
A mysterious creation that appears in Mega Man X5 within the confines of the virus area X and Zero investigate. Often considered the most difficult Devil boss in the entire franchise and one of the hardest bosses period, it is a much sturdier model and dishes out far more damage than one would give alarm for. While it continues the mass projectile tradition, it instead breaks its body up into a 4x4 column of pieces surrounded by an outline of its normal form which inflicts a great amount of damage if touched. Even after it has reformed, it will take some time adjusting as it has the ability to move its eye's position to any part of its body. Its eye can also fire off a projectile. It also has the ability to further change its form, morphing itself into the Wily Machine 6 to cover more ground and therefore making itself more dangerous. There could be a chance that wily had blueprints for the wily machine 6 lying around somewhere or wily created the shadow devil but this has not been confirmed, But it is likely for the devils where only used by wily in the classic series (not including the Grey devil or Dark moon).

Rainbow Devil
Even after a couple of centuries, the Devil design remained alive in the form of the Rainbow Devil, fought in the first Mega Man Zero as well as Mega Man Zero 2. Like the Green Devil, it was covered in an amorphous gelatin, but it was much more mobile and active with its attacks. Rather than splitting its mass into projectiles, it flung its pieces around by spinning in one place where the pieces would impact with a small explosion, but remained intact and would return to the main body. Also unlike the other Devils, it was controlled by a head rather than an eye, making it a rather special type of Pantheon.

Lava Demon
The latest known model, from Mega Man ZX, yet again controlled by a head rather than an eye. However, what separated itself apart from others was the usage of magma rather than a specially-made substance. Its design was decidedly more demonic in nature and significantly more advanced since it could control which parts of it were cooled down while the rest of it remained liquid. It often lurched towards enemies or alternatively, separating its mass into falling globs of lava before reconstructing a new body from the lava below.

Chaos Devil
This variant was developed by Drs. Eggman and Wily in the Archie Comics crossover Worlds Collide, fusing elements of Chaos with that of the Devil robots. It was virtually uncontrollable to anyone besides Eggman and Wily, and effectively acted as a dog while under their control.

Steel Devil
A Devil model from the Mega Man comic by Dreamwave Productions.