Ciel System

The Ciel System (システマ・シエル) is a new energy source developed by Ciel in the Mega Man Zero series. The system was named by Cerveau, the Ciel in the name being an acronym that stands for "Convergent Ignition by Energen Linkage".

History
The Ciel System was developed by Ciel in order to end the energy shortage from Neo Arcadia, also ending the dispute caused by it and the persecution of innocent Reploids. By analyzing Crea and Prea, Ciel was able to create the energy system within the two months between Mega Man Zero 2 and Mega Man Zero 3.

After its development, Ciel secretly sent a sample of it to Harpuia so they could end the war between the Resistance and Neo Arcadia. However, this was not possible due to the appearance of Omega and Dr. Weil. After Dr. Weil and Copy X obtained the Dark Elf by killing several humans, they tried to convince Ciel to give them the Ciel System to combine it with the Dark Elf to generate great amounts of energy, but Ciel refused as Weil could not be trusted. After Weil's defeat, the Ciel System solved the energy problems from Neo Arcadia and brought peace, becoming an important discovery that changes the very foundation of the world, and brings the field of energy research into a new era.

Characteristics
It is unclear what kind of energy the Ciel System is as it was not clearly depicted in the series. It is only known that its basic principle consists of using a small amount of Cyber-elf energy and having an Energy Crystal as a catalyst to produce great amounts of energy. Its creation is apparently related with the improvement of Cyber-elves in Mega Man Zero 3 and 4, as Ciel spent a long time researching them.

Trivia
While little is known about the Ciel System, it is often speculated that one or more of the following may be related to it:
 * As the music "System-a-Ciel" is used in Ciel's Amidakuji-like minigame from Mega Man Zero 3, it is believed that the minigame is based on Ciel working on the Ciel System, linking colored jewels to the right colored beaker to form it. When four jewels of the same color are combined, they form a crystal-like object similar to Refractors. A similar object can also be seen in the Baby Elf factory, in the room where Zero faces Cubit Foxtar, presumably being the sample Ciel gave to Neo Arcadia. However, it is also possible that those may be Energy Crystals with a different design or a different energy source.
 * Ciel's artwork from Mega Man Zero 3 has her with a flower-like shape near her resembling a Cyber-elf. It is believed that it is related to the Ciel System, as concept art from the New Resistance Base's command room contains a flower design and mentions that the room is powered by an energy created by Ciel. However, it is not visible in the game and the type of energy isn't specified.
 * While never mentioned in the Mega Man ZX series, it is assumed that the flower-like objects seen on the Slither Inc. HQ and in the Grand Nuage's engine room are related to the Ciel System, assuming that the flower in Ciel's artwork is indeed it. This is due to Serpent's company providing energy to the whole country and being credited for solving the energy crisis, and Ciel was the first commander of the Guardians. However, Serpent and his company would later stage Maverick outbreaks and take credit for saving humans and Reploids due to their controbutions to solving said energy crisis.