This papercraft is a Demon Sword (aka Demon Blood Sword), the sword that Joshua formerly owned, based on the American animated television series Adventure Time, the paper model was created by aiko-chan14, there are line and no-line two versions.
It is the family sword, and is the prize at the end of Joshua's dungeon, which Finn and Jake were sent to explore in the episode "Dad's Dungeon." It is made entirely out of Demon blood, as explained by Joshua in the hologram video that he made for Finn and Jake for future viewing. The sword has a Celtic cross on the guard. It was found in the last chamber of the dungeon, where Finn uses it to defeat the Evil Monster. It was locked up with chains and stuck in a formation of blue and green crystals when Finn found it; the key for it was around a monster's wrist. Instead of defeating the monster to get the sword, Finn ripped it from the crystals, breaking the chains, and subsequently used the sword to defeat the monster.
The Demon Blood Sword, is a rather unusual looking sword. The sword is in perfect condition, and is almost entirely blood red in color, except for the brown leather grip, and white spike on the end of the handle's pommel. Also, the white spike seems to have a small red cross on it. Strangely, the guard of the sword is shaped like a Celtic cross, with the handle of the sword being in place of the top part of the cross, and the actual blade in place of the bottom, or longest part of the 'cross'. The handle of the sword is also rather long, though the sword still looks balanced. Out of the three main swords Finn has used in the series, the Demon Blood Sword is the longest.
This sword replaced the Root Sword that Finn found in "Mystery Train." Finn uses this sword for the first time in the episode, "Return to the Nightosphere." It seems that the design for the sword was slightly changed for some episodes; the tip of the handle is white instead of red.
Even by sword standards, the blade itself has shown an immense amount of strength and durability. This is demonstrated in "Dad's Dungeon" when Finn used it to stab and lift the Evil Monster off the ground and toss it into a pit behind himself, and the sword did not bend in the slightest. In "Return to the Nightosphere," the sword is shown to easily resist the energy beams Marceline creates when in her 'blood mist form', despite the beams ability to destroy or transform near anything they hit. In "Vault of Bones" it is shown to be fireproof, as Flame Princess it able to wield it without consequence. [Source: wikia]
You can download the papercraft model here: Adventure Time - Demon Sword Free Papercraft Download