Velezark is the main antagonist of Fire Emblem: Warriors.
Velezark is an evil and powerful Chaos Dragon who led his Manakete and Monster forces to attack Aytolis, but 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 Velezark acts as a spy for King Oskar to steal the Shield of Flames, Velezark and Oskar intend to utilize the shield's power for their own sinister purposes.
Once 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. Darios and Oskar prepare to surrender their weapons, he will spare her. They retrieve their weapons, and Rowan forces Darios back as Lianna rescues Yelena.
However, Velezark lets Oskar fall into the circle. The king's body is absorbed to 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 is about to kill the twins, Darios 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.
Fire Emblem Gaiden & Echoes: Shadows of Valentia
The Black Fang
Fire Emblem: The Sacred Stones
Fire Emblem Awakening
Fire Emblem Fates
Fire Emblem Warriors
Tokyo Mirage Sessions ♯FE
Fire Emblem Heroes
Fire Emblem: Three Houses