This MLP papercraft is the Alicorn Amulet, based on the anime My Little Pony Friendship is Magic, the paper craft was designed by RocketmanTan. The Alicorn Amulet is a magical amulet that is featured in the episode Magic Duel. According to a book that the main characters find in Twilight Sparkle's library, the Alicorn Amulet blesses the bearer with "untold powers". However, the more the bearer uses the amulet, the more it "corrupts" him or her. The book goes on to say that the amulet has an in-built magical lock that prevents any pony other than the bearer from taking it off.
The amulet is first shown in Magic Duel, when a cloaked pony enters a curio shop and points to a glass jar holding the amulet. The storekeeper refuses and warns her of the amulet's dangerous nature, but changes his mind after she puts a large sum of bits on the table.
The cloaked pony goes to Ponyville wearing the amulet and reveals herself to be Trixie. Her eyes and magical aura glow red under the influence of the amulet. She challenges Twilight Sparkle to a magic duel. Twilight initially refuses, but agrees to the duel after Trixie continues her assault on the town.
During the last stage of the duel, Trixie performs an age spell on Snips and Snails, turning them into a foal and an elderly pony, respectively. Twilight is shocked by this, exclaiming that age spells are "only for the highest level unicorns". Twilight attempts to undo the spell, but her magic fizzles out. Trixie promptly banishes Twilight from Ponyville.
When Twilight goes to the Everfree Forest to practice magic under Zecora's supervision, her friends attempt to find the reason behind Trixie's new magical powers. In Twilight's library, they find a book depicting the Alicorn Amulet. The book says that the Amulet blesses the user with untold powers, but corrupts the user the more it is used. The Amulet also cannot be taken off by anypony other than the user.
Twilight returns to Ponyville to persuade Trixie to duel a second time, on the basis that Zecora has supplied Twilight with a far more powerful amulet from beyond the Everfree Forest. Trixie performs the age spell again, but becomes unsettled as Twilight seemingly performs the age spell on Applejack and Rarity, a duplication spell on Rainbow Dash, a spell that enables Pinkie Pie to play ten instruments at once, and a gender-changing spell on Applejack. Trixie seizes Twilight's amulet and takes off the Alicorn Amulet, believing she can conquer Equestria with her newfound power, and while still exalted with her success, Rainbow Dash takes the Alicorn Amulet from her and puts it in a wooden box, saying it needs to "go into hiding where it belongs". After that Twilight tells her that her amulet is just a fake decoy that was crafted with one of Zecora's necklaces and doorstops. [Source: wikia]
You can download this paper craft template here: My Little Pony - Alicorn Amulet Free Papercraft Download