Leviathans (Marvel Cinematic Universe)

The Leviathans are giant flying mechanical creatures that aided Loki and the Chitauri in the invasion of Earth. They also serve as the secondary antagonist in The Avengers movie. The Chitauri served as rides for the Chitauri as they rode on them as scout ships.

History
After Loki acquired the Tesseract, he had Eric Selvig invent a device to contain its power and to use it to open a portal in the sky above Stark Towers. The first Leviathan appeared after dozens of Chitauri arrived on Earth. Stark managed to catch its attention by shooting a dozen missiles at its face. As the Leviathan chased after Tony, Tony leads it to Bruce Banner, who transforms into the Hulk and manages to kill the Leviathan by punching it in the face, stopping it dead in its tracks. After Loki watched its demise, he was unsurprised by it as he orders the Chitauri to summon the rest, revealing dozens of more Leviathan appearing from the portal.