This picture shows that the Night King is riding Viserion Dragon to attack all the living. Viserion was one of the three dragons born in the wastelands beyond Lhazar, along with Drogon and Rhaegal. He was named after Daenerys Targaryen’s elder brother, Viserys. After the death of Viserion Dragon, the Night King turned Viserion to an Ice Dragon. he lost his free will and was enslaved by the Night King. He was also able to breathe fire that was capable of melting the Wall, though it was blue in color. In this picture it clearly proves that Viserion is also belongs to the army of death because his wing are torn from some places, normally a living dragon can’t easily fly when their wings are torn. And it shows that Viserion is more stronger after it’s death than the living dragons.