Tenkai Knights Season 1 Episode 13 Vilius Unleashed

Following the battle located in the Dragon's Nest, Guren and Chooki travel to Quarton with Boreas the five Cubes are combined into one giant cube that can be only opened with the Dragon Key, awakening the Tenkai Dragon. However, Dromus captures it in a trap and transports it to the Corrupted headquarters. During the fight, Guren reveals his human identity to Vilius before destroying him. In the aftermath, Vilius revives and swears to conquer Quarton and Earth.