Model W

Model W, known as Model V in Japan, is a Biometal from the Mega Man ZX series. It is the soul of Dr. Weil - 'The Evil Mega Man'.

Background
Centuries before the events to the series, a madman tried to conquer the world by building a giant battle station in space called Ragnarok. That man fused with Ragnarok, but he was ultimately defeated by a legendary hero. The space station broke apart in the battle and burned as it fell through the atmosphere.

However, the soul of that man is contained in the remaining fragments of Ragnarok and Master Albert creates Model W from this combination. Knowing the properties of Model W, Albert devises a plan to remake the world using the power of the Biometal.

As part of Albert's scheme, Model W's power is locked to Albert's own DNA, making it so that only those with the same genetic code will be able to unleash Model W's power. The hidden pieces of Model W (referred to as Model Ws) start to create Mavericks with their corruptive influence, feeding on the fear instilled by the Mavericks on humans and Reploids alike until they are fully awakened. In order to facilitate the process, Albert orchestrates the Game of Destiny by creating two sibling Reploids: Prometheus and Pandora. After merging them permanently with Model W fragments, Albert commands the two to determine the strongest Mega Man. The ones chosen by Prometheus and Pandora are eventually infused with Albert's DNA, allowing them to use the power of all Biometals, including Model W.

A small Model W fragment is one day discovered by the first commander of the Guardians, who were searching for the source of the continuous Maverick outbreaks. Uncovered as the source of Maverick activity, a Guardian unit led by the commander studies the fragment. However, the members begin to suffer strange symptoms such as headaches and numbness. The commander decides to dismiss the unit and resume the research on her own, but the Guardians are betrayed by one of their own: Serpent, who is driven mad by Model W and steals the fragment, becoming "something else." The unit fights Serpent in hopes of buying their commander time to escape, succeeding at the cost of their lives.

Recognizing Model W and its threat, the first commander uses data from Model W itself to create six new Biometals to counter it: Model X, Model Z, Model H, Model F, Model L and Model P. Afterwards, she locates the core of Model W in Area M (Remains) and seals it away, giving the passwords to the Biometals in hopes that a person capable of destroying Model W will appear.

Mega Man ZX
Unfortunately, the sealing of the Model W core does not stop the Maverick outbreaks. Serpent, now regarded as a national hero for solving an energy crisis, is approached by Prometheus and Pandora who give him further information about Model W and the Game of Destiny. Since then, Serpent is said to dig the Outlands like a possessed man, searching for the Model W core while instigating more Maverick raids to gather the Cyber-Elves to feed it. In the process, Serpent comes into possession of Model H, Model F, Model L and Model P, taking their passwords and using them to create Pseudoroids to assist him. When the Mega Man Model Z Girouette attempts to fight one of the raids with the aid of either Vent or Aile, the Mega Man Model X, Serpent uses his Model W fragment to corrupt Giro and turn him against his friend. Giro is taken out by Serpent, now accompanied by Prometheus and Pandora, and the passwords from Model X and Model Z are stolen. Vent/Aile only survives the encounter by combining Giro's Biometal with Model X, transforming into Mega Man Model ZX.

Although the protagonist is able to recover the other four Biometals from Serpent's Pseudoroids, Serpent succeeds in locating and retrieving the Model W core, awakening it with the Cyber-Elves of the raid victims. However, the final key to the core's awakening actually comes from Vent/Aile, whose hatred for Serpent serves to complete the process. With the core fully awakened, Serpent merges with it, becoming a to become a gargantuan mechanical abomination which continues to transform. However, Mega Man ZX fights Serpent with renewed resolve and wins the battle. The Model W core is shattered as a consequence and the pieces wind up scattered across Cinq Ville.

Mega Man ZX Advent
Four years and eight months after the first game, the threat of Model W continues. Sometime during that period, Model H, Model F, Model L and Model P are stolen by Prometheus and Pandora, then given to four new Mega Man: Aeolus, Atlas, Thetis and Siarnaq. The four carry on the Game of Destiny, retrieving the Model Ws as they are awakened despite interference from the new Mega Man Model A (Grey or Ashe depending on the player's choice). The four are assisted by new Pseudoroids created by Albert with Model W fragments as their cores.

When Master Albert is discovered to be the man behind Model W, and that the original Model W core wasn't quite as destroyed as previously believed, he immediately starts multiple Maverick attacks to awaken the remaining Model Ws as quickly as possible. The pieces of the Model W core broken in the battle with Serpent also cause anomalies such as anti-gravitational effects in the forest and the melting of the frozen Scrapyard. Although the Model A Chosen One defeats Albert's forces, and even destroys a Model W after it merged with a Mechaniloid, the remainder are eventually gathered in Albert's undersea base.

Albert is ambushed by Prometheus and Pandora, who always despised Albert for imposing a life of endless servitude on them. However, this overwhelming hatred ultimately awakens all the Model Ws, just as how Vent/Aile's hatred for Serpent was used to awaken the core. The fragments begin to merge almost immediately, forming the ultimate Biometal: Ouroboros.

As Ouroboros rises from the sea, a Maverick army is unleashed by Albert to lay waste to the world so he can remake it as he sees fit. Assisted by Mega Man ZX and the Guardians, Mega Man Model A breaks into Ouroboros and finally confronts Albert, who had previously deceived Prometheus and Pandora with a decoy. Claiming to be the ultimate Mega Man, Albert reveals the real power of Model W: every spirit devoured by Model W lives on inside Albert; combined with his own A-Trans, Albert gains the ability to incorporate these souls, effectively giving him the power to control life. With this power, Albert's goal is to create a new world, bringing new life and controlling its future. However, even this power does not stop Grey/Ashe from defeating the ultimate Mega Man. This battle results in the destruction of Ouroboros, which explodes in the sky and vanishes in the sea without a trace.

Although Model W is believed to be finally destroyed for good, this has yet to be truly confirmed.

Power and Abilities
It should be noted that the real Model Ws were pieces of Ragnarok, and that the ones that resemble Dr. Weil's form are only mass-produced fragments that Albert made (of which at least seven exist, with Prometheus, Pandora, and Serpent each holding one, and Master Albert holding the rest, not to count the eight Model W Pseudoroids). Albert's Model W fusion is also very similar to Model A, as it can use Chronoforce's Time Bomb to cancel out Grey/Ashe's, as well as mimic all of the other Mega Men's special attacks, and has its own homing shots, albeit stronger. This is because Model A and Grey were made to be Albert's backup system in case something should happen to him before the "Destiny of Destruction" was seen through. In effect, Albert's Model W is also built to counter Model A's A-Trans, as the easiest way to neutralize his shields is by targeting all the fragments with Model A's homing shot. Albert can perform all of his attacks, both copied and original, in his own transformed state, whereas Mega Man Model A must take the form of the attacks original user. In this regard, Albert's abilities are more similar to those of Mega Man X, which gives another kind of significance to the title of "Ultimate Mega Man".
 * Main Articles: Serpent, Albert

Even without a megamerge, the Model Ws are also capable of causing feats that would be considered unnatural, including causing an imbalance to gravity or reactivating/enhancing deactivated machines.

Trivia

 * To date, Model W is the only Biometal with the soul of a human.
 * Also, Model W is the only Biometal which player can't even control for once in the whole series.
 * In Mega Man ZX, the Model W stolen by Serpent is referred to as a "fragment". In Mega Man ZX Advent, every part of Model W is called such, even in plural.
 * Ouroboros is shaped after the eponymous symbol of eternity.
 * The power of Ouroboros combined with Albert's own A-Trans harkens back to Dr. Weil's original expertise: Reploid ressurrection. Incidentally, Spidrill Neo is an example of Model W's ability to merge with destroyed Mechaniloids, reviving them while also powering them up.
 * When escaping either Grey or Ashe for the first time, Albert uses four Model Ws (resembling the one Serpent had) to block Model A's homing shots and fly away. He does not actually perform Megamerge with any of the Model Ws.
 * The orange horns are a defining feature of Model W's appearance. In fact, the horns also resemble the orange glass that once covered Dr. Weil's head.
 * According to Siarnaq in Ashe's storyline, Model W has multiple levels of awareness; this was previously suggested by a report from a Guardian recon unit seen in Mega Man ZX, and even Ashe claims that Model W has taken control of Albert.
 * Likewise, during the same event, Siarnaq stated that after Model W reaches level 2 awareness, it will start generating mavericks, one every 5717 seconds (1 hour, 35 minutes, and 17 seconds).