The Amulet of Raiden is a mystical talisman that belonged to the Earthrealm's thunder god, Raiden.
This golden, sapphire amulet with the Mortal Kombat dragon icon was originally created by the Elder Gods and was given to Raiden as a gift. Raiden had his amulet with him during the original timeline, until the Battle of Armageddon.
During the Mortal Kombat (2011) Story Mode, a future version of Raiden, while fighting a losing battle against Shao Kahn, uses the shattered remains of his amulet to send his past self visions of the future, as well as the message "He must win."
Throughout the game, Raiden periodically checks his amulet, noticing it cracking more and more as the events progress - indicating that the future he seeks to prevent is drawing closer despite his efforts. Near the end, the amulet is shattered by Shao Kahn just as it was in the future. After the defeat of Shao Kahn, the amulet is restored to its intact self, indicating that the future has finally been changed.