Ciel

Doctor Ciel (シエル) is a fictional character in the Mega Man Zero video game series. Although not a playable character, she is considered the female lead and heroine of the series, having important roles in most of her appearances, effectively making her the Zero version of Roll.

Appearance
Ciel is a young girl (14 years old in Mega Man Zero) with a modest stature. She has fair skin, cobalt blue eyes and long blonde hair with three angular bangs, usually tied into a ponytail. She wears a pink outfit made of a helmet, a sleeveless dress, a Resistance vest, plated high heels and white gloves. The helmet has a hole on the back for the ponytail, and a retractable white visor. She also has winter clothing composed of a long pink jacket and thick boots.

Personality
Ciel is a gentle, kindhearted person who is always concerned about the welfare of others. She has an issue with insecurities as a result of Neo Arcadia's pressure on the Resistance, but Zero's continued support gives her the motivation to move forward. She cares greatly about Zero and often regrets requesting his help for dangerous missions. She is also close to Alouette, having named the girl and given her the stuffed animal she is always carrying.

Despite her age, Ciel is a genius scientist, being capable of creating a replica of X merely by observing the methods used to create the Four Guardians. Her study of Cyber-elves also allows her to develop a new energy source in the Ciel System, an important discovery that starts a new age in the field of energy research. Ciel believes in solving problems not through fighting, but through the power of science; she can be very dedicated to her research, to the point of staying up late. Ciel also has an emphatic connection with Cyber-elves, and illustrations often depict her alongside them in order to reflect this.

History
According to the "Mega Man Zero Official Complete Works" source book, Ciel is a product of Neo Arcadia's technological advancements, which is what allowed her to attain such a high level of knowledge at such a young age. With the goal of creating an utopia for humans and Reploids, Neo Arcadian researchers began to produce humans with altered DNA. Some of these humans were children born specifically to develop better Reploids to assist in the research. Ciel was one of these children, and stood out as a prodigy. Ciel became a Reploid researcher that worked for Neo Arcadia. When Mega Man X disappeared eight years before the events of Mega Man Zero begins, Ciel created Copy X to replace him. Amazingly, Ciel is aged 14 during Mega Man Zero, which means she built Copy X at the age of 6, making her a child prodigy. Additionally, one of her ancestors, another female scientist, was apparently directly responsible for the creation of the original Mother Elf, from which all other Cyber-elves were spawned.

However, when the Neo Arcadia government began oppressing and executing Reploids to solve their energy crisis, Ciel migrated with Reploid refugees to a ruined city when she was 9 years old. Knowing they were being falsely accused, and that the one behind it all was her own creation, she felt guilty and decided she could not stand by helplessly, and she soon became somewhat of a mother figure to many of the Reploid refugees, particularly a young girl she named Alouette. Times grew more desperate, though, and she eventually found her only hope to be uncovering a legendary hero that most people didn't even believe in anymore: the legendary Maverick Hunter Zero. She sought and eventually found him, though it took the sacrifice of one of her Cyber-elves, Passy, to wake him up.

Mega Man Zero
Zero, whose memory was blank possibly due to "hibernation sickness", helped Ciel escape and then helped her with several missions for the Resistance. He kept protecting her dutifully, until he finally brought down Copy X. Zero was separated from the Resistance when he barely escapes the destruction of Copy X's sanctum.

After the fall of Copy X, Ciel and her band of Resistance members left their ruined base and joined up with another opposition group. Since that time, she has set herself to work on discovering a new source of energy to bring about peace, and handed off the reins of running the Resistance off to Elpizo. With Zero's return to the Resistance, she redoubled her efforts to bring about peace.

Mega Man Zero 2
During the time period covered in the second game of the Zero series, Ciel researched the possibility of using two Baby Elves as a source of energy. This system was not completed until some time between the second and third games, and was called the "Ciel System", known as "System CIEL" (Convergent Ignition by Energen Linkage) in Japan. Also, in a conversation with Alouette, Ciel was supposedly saddened when departing the first Resistance Base. Although the reason is never revealed, some speculate that it has something to do with Zero's disappearance.

Ciel is reluctant to allow then Resistance commander, Elpizo, commence "Operation Righteous Strike", where Elpizo leads a strike force to destroy Neo Arcadia (believed to have weakened due to the absence of Copy X). Her fears came true when the operation turns out to be a disaster, with most of the Resistance troops involved having been killed, except for Elpizo. Having been driven mad by his defeat, Elpizo leaves the Resistance in search of the Dark Elf, and Ciel resumes command afterwards.

Elpizo went on to search for the Dark Elf, hoping to give him the power to rule the world. To do this he had to break the seal that is sealing the Dark Elf, X. Elpizo finds X's body and destroys it. Zero subsequently defeats Elpizo and the Dark Elf, instead of killing Elpizo, heals him and he is turned into what seems to be a Cyber-Elf.

Mega Man Zero 3
By the beginning of the third game, Ciel had completed the self-titled Ciel System and had sent the ruling body of government of Neo Arcadia notes describing the new energy system. Shortly after this, the scientist Dr. Weil assumed control of Neo Arcadia and attempted to force her to give him the system. Ciel refused to answer Weil's demands (after the latter's earlier action where he directed a missile towards a populated area, just to capture the Dark Elf). Zero once again protected her and the Resistance from the forces of Neo Arcadia. Though defeated, Weil still controlled Neo Arcadia.

Ciel, at the time between Mega Man Zero 3 and 4, decided to split the Resistance Base into two, the other into a mobile unit, able to travel to wherever they were needed. Zero, Ciel, Cerveau, Faucon, Hirondelle, Rouge, and Alouette went on the mobile unit, while the others remained in the main base.

Mega Man Zero 4
As the fourth game began, Ciel, Zero, and the Resistance came across a human caravan fleeing Neo Arcadia. It is then explained by Neige, leader of the Caravan, that Dr. Weil controlled Neo Arcadia since Copy X's departure, and that they escaped because the once human nirvana had become dangerous thanks to Weil's rule. Even though the human refugees didn't appreciate their help, partially because of the Resistance having comprised mostly of Reploids, Ciel asked Zero to aid them anyway. Ciel helps Zero to stop Weil's new device, the Ragnarok, from destroying the new human encampment at Area Zero, which also happened to be where the Eurasia Colony fell at the end of Mega Man X5. After a lengthy battle with Weil on the Ragnarok itself, they manage to save the humans and free Neo Arcadia from the clutches of Dr. Weil.

With this, peace between humans and Reploids had finally been achieved after their hundreds of years of war. However, the price was heavy as Zero (supposedly) dies on Ragnarok when it breaks apart and burns to bits in the atmosphere. Despite Zero's habit of resurrecting, it is assumed by many that it's decidedly impossible for him to have survived this time. Also, there is no need for him to fight anymore, since Zero had finally achieved the ultimate peace that he and X had been fighting for ever since the beginning.

During the fourth game's credits, Ciel falls on her knees and cries from Zero's apparent death as Ragnarok's pieces fell from the starlit sky. At the credits' end, she stands up strong and dries her tears, promising to the missing Zero that she would not let his action be in vain, and that she would keep the eternal peace between humans and Reploids that Zero had finally been able to create. She then finalizes by saying that she knows Zero is still alive somewhere, and that she knows he will come back because she believes in him.

Mega Man ZX
In Mega Man ZX, it is revealed through recovered Data Disks that Ciel went missing shortly after discovering Model W and creating the six Biometals in response. Ciel is also revealed as the sister of Prairie, the commander of the Guardians, though they are not biological sisters. It is strongly hinted that Prairie is actually Allouette, due to this relationship with Ciel being identical to Allouette's, as well as general similarities between Prairie and Allouette's character designs. In particular, they carry the same stuffed animal. Also in ZX, Ciel is also shown always wearing the winter coat she wore in the beginning of Mega Man Zero 3, with no apparent explanation of why she does so.

In the manga
Different from her personality from the games, in the Rockman Zero manga Ciel is unpredictable and can be very aggressive, but she still cares for the others. She first appears being mentioned in chapter 2 by a Reploid, and first meets Zero in chapter 4 helping him to escape from Pantheons. Later, they are attacked by Leviathan, and Zero's weapons didn't work on her ice dragon. Ciel gave Zero a fire sword that helped him defeat the dragon, and Leviathan escapes. After this, Ciel takes Zero to the Resistance, where they are attacked by Fefnir. Ciel feels sad for her friends that died in the battle, especially when Passy supposedly died when used her power to recover Zero from his wounds. After they escape the base, Rockman Zero and Ciel takes different directions, as he doesn't want to join the Resistance. After Neo Arcadia is defeated, she appears shortly talking with her older sister, Cial, the ruler of Neo Arcadia. Copy X only appears in the manga as an unnamed fusion of the four guardians.

Trivia

 * Ciel was only 6 years old when she created Copy X, and she was able to create him by watching and mimicking the same experiments that gave birth to the Four Guardians. The idea and explanation for this notable feat had to be figured out quickly by Inti Creates when they decided to change the final boss of Mega Man Zero from the real X to a copy. Then she was decided to be a genetically modified child from Neo Arcadia.
 * Ciel was originally intended to be a cyborg.
 * Ciel is one of the few human main characters in the main Mega Man timeline; like most of them, she is also a scientist.
 * Throughout the series, Ciel is shown to have romantic feelings for Zero, regardless of the fact that he's a Reploid and she's a human (such as in the ending of MMZ4 she says "I" then hesitates before continuing "I believe in you" possibly signifying she was going to say "I love you").
 * Ciel holds a few notable similarities to Dr. Light of the Classic series. Aside from both being pacifistic scientists of their time, they provide aid for the heroes generations in the future (Light provided the armor upgrades to X and Zero; Ciel created the 6 Biometals).
 * Ciel bears a slight resemblance to Iris Sepperin, a character from the Japanese doujin soft series, Rosenkreuzstilette. In-universe, she is most notable for her resemblance to the numerous incarnations of Roll as well as Alia.
 * The resemblance to Iris is quite ironic, as Iris is much closer as a character to the likes of Copy X and Dr. Weil, and is in fact the arch enemy of Grolla Seyfarth, a character with many allusions to Zero.
 * A woman resembling Ciel appears in Mega Man ZX Advent, in the stained glass in the background of the 8 bosses rematch in Ouroboros.