This papercraft is a Power Sword for Howling Banshee, a Power Weapon that has been shaped into a sword of varying lengths and designs crafted from one of any number of different materials, though usually Adamantium, from the Warhammer 40K series, the paper model is created by Dima Logvinov.
When its power cell is activated, often by touching a control located on the hilt, the blade is sheathed in a lethal corona of disruptive energy. This energy field allows the blade to carve through flesh, bone and most forms of armour plate alike, making a Power Sword a highly effective Imperial close combat weapon. Power Swords are used by all members of the Imperial armed forces, including the troops of the Imperial Guard and the Space Marines of the Adeptus Astartes. Xenos races such as the Eldar, their evil kin, the Dark Eldar and the Necrons are also known to make use of such weapons. [Source: wikia]
You can download this papercraft template here: Warhammer 40K - Banshee Power Sword Free Paper Model Download