Velezark

Velezark (イビルザーグ, Evilzerg in the Japanese version) is the main antagonist of Fire Emblem Warriors, serving as the final boss and mastermind behind the events of the game. He leads the Salamander and Fafnir Manakete forces, in addition to controlling monsters like Outrealm Fiends.

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Velezark is an evil and powerful Chaos Dragon who is capable of manipulating time and space and completely consuming dimensions. Long before the events of the game, Velezark led his Manakete and Monster forces to attack Aytolis, but was sealed away by the power of the Shield of Flames wielded by the Sacred Dragon queen of the Divine Dragons. However, the sudden appearance of Outrealm portals throughout the kingdom of Aytolis indicated his return.

Velezark first appears briefly at the end of Chapter 14, trapping the Gristonne prince Darios inside the castle tower in the Fortified Citadel and possessing him before being found by the Aytolis siblings, Rowan and Lianna, and their allies from the three worlds.

While holding control over Darios' body, Velezark acts as a spy for King Oskar to steal the Shield of Flames once it's become fully powered up, as well as to bring Darios back onto Gristonne's side. Velezark and Oskar intend to utilize the shield's power for their own sinister purposes.

Once each of Gleamstones are gathered for the Shield of Flames in Chapter 16, Velezark takes control of Darios' body and uses it to steal the Shield of Flames from Rowan and Lianna's group. It's also revealed that Velezark and Oskar have Queen Yelena as their hostage.

The Velezark-possessed Darios and Oskar prepare to sacrifice Yelena to revive the evil dragon's body, though Velezark (while in Darios' body) makes a proposal: if the twins surrender their weapons, he will spare her. When they do so, he turns to kill her anyways, but is stopped by Takumi, who predicted this outcome. The twins retrieve their weapons, and Rowan forces Darios back as Lianna rescues Yelena from the magic circle she was being held captive in.

However, Velezark had a back-up plan, and kills Oskar after he approaches him. Explaining that he only needs royal blood to activate the magic circle, he lets Oskar fall into the circle. The king's body is absorbed to revive Velezark's power and body. As the twins believe Darios can fight Velezark's control, Darios and Velezark began to fight over the former's body from the inside, leaving the twins to defeat him. Despite Darios' pleas for the twins to kill him quickly before Velezark returns, they refused, believing there is another way to save him.

However, Velezark separates from Darios and manifests his dragon form, regaining his full power. As Velezark is about to kill the twins, Darios sacrifices himself to save them and returns the Shield of Flames before falling victim to the collapsing castle. Afterwards, Velezark escapes to the World Tree, awaiting the twins' arrival for the final battle.

In the end, Velezark is destroyed for good, his body disintegrating upon his death.

Trivia

 * Velezark seems to take from past Manakete and Dragon antagonists like Medeus and Anankos. Like the former, Velezark rules over Manaketes of different Dragon tribes and like the latter, he possesses a mentor of the Hero before regaining his full power.
 * Velezark's name is a portmanteau of Veles, the Slavic god of magic, earth, and water, and "dark". This connects Velezark to Medeus, Anankos, Idunn, Grima, and Loptyr, all major Dragon antagonists from prior games in the series.