This mecha paper model is Death, the ruler of the Land of the Dead in the episode "Death in Bloom" and the Dead World, as seen in "Sons of Mars", based on the American animated television series Adventure Time, the papercraft is created by WebDude.
In his first appearance, Death plays the double-bass drums in a competition against Finn. He almost kills Finn, but gives back Jake's memory and the life of Princess Bubblegum's plant after Finn mentions Peppermint Butler. Death is shown to have various powers, such as the "Kiss of Death," encasing people in force fields, and sending people back to the Land of Ooo. [Source: wikia]