This papercraft is Nightingale Blade, a leveled, unique, one-handed weapon that appears in the game The Elder Scrolls V: Skyrim, the paper model is created by ZombieGrimm. The finished model measures about 36 inches long. The Nightingale Blade once belonged to the Nightingale and former Thieves Guild Guildmaster Gallus Desidenius.
Karliah gives the blade to the Dragonborn as a reward for completing the Thieves Guild quest Hard Answers. The Nightingale Blade can be upgraded with an ebony ingot with the Arcane Blacksmith perk. However, it does not benefit from any Smithing perks. This means that the weapon cannot be improved past its original quality without boosting the Smithing skill over 100. This can be achieved by using enchanted apparel or blacksmith's potions to Fortify Smithing. [Source: wikia]
You can download the papercraft model here: The Elder Scrolls V: Skyrim - Nightingale Blade Free Papercraft Download