This mecha paper model is The Enchiridion (Book), which translates to "The Handbook" or "The Manual", an ancient book with codes of conduct, guidelines, and other helpful information for heroes from the American animated television series Adventure Time, the papercraft is created by WebDude.
The book had great power which allowed it to tear open worm holes between dimensions in the multiverse. It was broken into pieces after turning to stone by Finn in "The Lich" in order to stop the Lich from gaining access to the multiverse, but, as it turned out, by doing this Finn made the portal to the multiverse. For more information please click here.
You can download the papercraft template here: Adventure Time - The Enchiridion (Book) Free Papercraft Download