This mecha paper model is Leviathan, named after the biblical sea monster Leviathan, and thus a counterpart to the Behemoth, from the animated television series The Big O, the papercraft is created by WebDude.
Most likely activated by Schwarzwald, the Leviathan's 4 claws can be energized and turn anything that it touches into sand. It appeared to have been called into the city by Dorothy when she began to speak in the same rapid and indiscernible manner as when she confronted the Archetype. Its purpose did not appear to be overtly destructive; its goal seemed only to be to incorporate Dorothy into itself. It was defeated when Big O turned its own energized claws against itself.
Schwarzwald is attempting to spread terror by showering the city with the foretelling of his latest declaration of truth and the discovery of a sand dragon megadeus, known as the Leviathan. Roger is hired by Alex Rosewater to track him down and foil the impending doom that awaits Paradigm City. After Dorothy takes piano lessons under R. Instro, he invites her to a church where he is now an organist. Roger finds a recovered megadeus at the end of a tunnel underground. This megadeus, revealed by Alex, was the Big Duo that was wrecked when Roger was battling Schwarzwald from before, but now it will be modified using the wreckage of another megadeus, which will then be created into something much greater. The city is being tormented by the Leviathan, and Roger is unable to use his communicator wristwatch because he is in an electromagnetic field. Dorothy tries to resist having to link herself with Leviathan, yet the Big O suddenly comes out and fights back. Roger, reaching the megadeus with Dorothy, then destroys the Leviathan. Angel later tells Roger and Dorothy that Schwarzwald was dead long before the Leviathan wreaked havoc upon the city. [Source: wikia]
You can download the papercraft template here: The Big O - Leviathan Free Robot Paper Model Download