This blade papercraft is designed by sgonzales22. The Kingdom Key is the most recognizable and the first Keyblade to appear in the Kingdom Hearts series, and is the form used in almost all depictions of the weapon. It has appeared somewhere within every game in the series. In Kingdom Hearts 358/2 Days, it can be upgraded to the Kingdom Key+ and the Kingdom Key++.
The Kingdom Key draws out the true power of Sora's Keyblade, even though it is not the strongest Keychain. As such, it is the true form of his Keyblade, which means that it is also the default form of Roxas's and Xion's Keyblades. The Kingdom Key is not wielded by Sora exclusively; Riku, Roxas, and Xion have also used it, and King Mickey is often seen wielding the Kingdom Key D, a color-inverted version of the weapon.
For Roxas and Xion, the Keyblade they wield is in fact Sora's Keyblade, existing in multiple places at once. Roxas also obtains a second Kingdom Key after absorbing Xion. The Kingdom Key D, a color-inverted Kingdom Key which King Mickey wields, is in fact the Keyblade from the Realm of Darkness, which he obtained to mirror Sora's Keyblade from the Realm of Light.
You can download this Kingdom Hearts paper model from here: Kingdom Hearts - Kingdom Key keyblade [Life Size] Free Papercraft Download