Dark Elf

The Dark Elf (ダークエルフ) or Mother Elf (マザーエルフ) is a Cyber-elf in the Mega Man Zero series, that serves as a minor antagonist in Mega Man Zero 2, and the quaternary antagonist in Mega Man Zero 3.

Appearance
Appearing similar to a normal Cyber Elf, the Dark Elf possesses wings similar to those seen on others (a good example being Passy). In fact, the only real "dark" aspect of her usual appearance is the shell around her normal body, suggesting early on that the curse placed by Weil is simply a shell to change her functions.

Personality
The Dark Elf doesn't seem to have much of a personality other than the fact that it knows little more than destruction and death. She does, however, speak of Zero, and it almost seems that she is calling Zero to do something, perhaps to help her. At the end of Mega Man Zero 2, she turned good briefly to allow Elpizo to survive in the form of a Cyber Elf. This trait in itself shows the Dark Elf's true personality shining past her wretched curse. During Zero 3, more of this personality was shown as the curse was finally broken.

It's implied that the Dark Elf hates Dr. Weil for what he did to her. In the scene where she transforms the Aqua Pantheon into a Dark Elf variant, she shouts "Stooooop iiiiiit!" when it tries to capture her (since it was trying to capture her for Dr. Weil, allegedly for Neo Arcadia's benefit).

History
The Mother Elf was created as the ultimate weapon during the era of Cyber Elf development, towards the end of the Maverick Wars, the conflict that lasted throughout the Mega Man X (series). As revealed in Mega Man Zero Official Complete Works, she was created from the Maverick Virus data in ZeroXorZ's body, as a "Sigma Antibody Program" capable of counteracting the Maverick Virus and Sigma's DNA. This was not the first attempt made to counteract the threat of the Virus; however it was the first of such attempts to actually be successful on a large scale. According to legend, Mega Man X used the power of this Elf to finally destroy the Maverick Virus' negative attributes, thus erasing Sigma from existence for good, ending the Maverick Wars. The fighting did not cease, however.

Following the construction of Neo Arcadia, the Elf was stolen from a laboratory by the evil Dr. Weil, who reportedly placed a "curse" on her. Dr. Weil then used her to instigate what came to be known as the Elf Wars. As revealed in Mega Man Zero 3, this tumultuous period was so violent that 90% of all Reploids and 60% of all humans were killed. X and Zero together stopped Weil and his reploid Omega, and after Zero went to sleep for 100 years, X sealed the Elf away at the base of Yggdrasil using his own body as the seal.

The Elf then disappeared into myth and legend along with Zero for 100 years, until the commander of the Resistance, Elpizo, sought to gain the power of the Elf during the events of Mega Man Zero 2. This quest led Elpizo to seek out the two Baby Elves, which in turn led him to an area deep inside Neo Arcadia, where he destroyed the original X's body and released the Dark Elf. The Elf gave Elpizo powers, but not enough with which to defeat Zero. After healing Elpizo and turning him into a Cyber Elf, the Dark Elf vanished after faintly saying "...Zero...".

The Dark Elf was seen again in various forms of prominence during Mega Man Zero 3, mostly tying into the mysterious Dr. Weil. It was Neo Arcadia's goal to recapture the Dark Elf, and Dr. Weil, in exile because of his crimes, returned with his creation Omega under false pretenses of helping Neo Arcadia capture the Elf, when all he really wanted was to use the powers of the Elf for his own purposes. Zero saw through the facade, and defeated Weil's reconstructed Copy X while hunting the Dark Elf. At the end of his journey, Zero encountered the Elf once more, in which it powered up his original body (inhabited by Omega). Upon Omega's ultimate defeat, the curse of Weil was finally broken, and the Dark Elf became good once again. She protected Zero from the explosion caused by Omega's destruction, and took him back to the Resistance Base. What happened to the Mother Elf afterwards is unknown.

Powers and Abilities
As the "mother" and original Cyber Elf, the Dark Elf's powers are immense, far surpassing those of other Cyber Elves. Developed originally from the Maverick Virus and subsequent anti-bodies of Zero, the original carrier of this epidemic, she was meant to serve as cure for both the Virus and its mutations and so far served as the only effective cure for it. This is achieved through her ability to completely re-write and restructure Reploid DNA codes.

While her original purpose was solely to cure the Reploids, she also displayed other numerous abilities. Due to her ability to re-write Reploid DNA, she can drastically enhance and empower a Reploid's abilities as well as change their physical appearance. Low-level or even non-combat model Reploids (such as Elpizo and a Pantheon Aqua-model) are transformed into extremely dangerous war machines by her powers. She can also repair and recharge a Reploid as seen with Omega during his fight with Zero. (These abilities are similar to those of the three types of Cyber Elves used in the games, though on a much higher level). She can even convert a Reploid into a Cyber Elf as seen with Elpizo after his defeat at Zero's hands. Despite all these powerful abilities, the Dark Elf's most frightening trait is her ability to completely control any number of Reploids within a certain range of it. (Though Zero and X were unaffected by this remote control). It's unknown how much of these powers are by-products of its original power, and how much was caused due Weil's tampering with her programming.

Overall the Dark Elf's powers were extremely difficult to control. Any Reploid who attempted to draw from her powers was corrupted and driven insane as seen with Elpizo during his second transformation. Only Omega (a Reploid constructed from Zero's original body with enhanced abilities) was able to draw out her full powers, not only explosively increasing its already great powers, but also greatly boosting the range of the Dark Elf's remote control powers to turn nearly all the Reploids in the planet into Weil's obedient pawns.

Trivia

 * In Mega Man Zero 4, when Dr. Weil uses the attack where he summons his Numbers, the sphere that he was holding bears a resemblance to the Dark Elf.
 * According to "The Three Keys to Solving the Mystery of Zero and Omega" section of the Complete Works, the Mother Elf was created by a female ancestor of Ciel, who used properties and samples of the Sigma Virus to create the Mother Elf. However, the effects of the Sigma Virus also overwhelmed the Mother Elf, causing her transformation into the Dark Elf. This section also includes a disclaimer noting that the information comes from the early concept phases of the Mega Man Zero series and therefore may not be canonical. Therefore, these details may not reflect the final product and future releases.