Mortal Kombat introduced an object that sets up a future story similar to the Infinity Gauntlet saga, which the MCU's Avengers: Infinity War and Avengers: Endgame are based on. Shang Tsung, one of the most powerful characters in the Mortal Kombat franchise, serves as the main antagonist of 2021's Mortal Kombat, where he exacts his plan to invade Earthrealm without creating another Mortal Kombat tournament. However, Shang Tsung could have accomplished much more than that had he sought the powerful Shinnok Amulet.
When Liu Kang gives Cole, Sonya, and Kano a tour of Raiden's temple, Kano sneakily gets his hands on a round golden artifact with an emerald stone embedded in it. This is the Amulet of Shinnok, an object capable of enhancing any fighter's abilities to godlike levels, trapping enemies inside it, and creating portals to any realm. Liu Kang realizes Kano stole it and orders him to return it, but it's never confirmed whether Kano actually complied. The artifact never comes up again, and the movie ends with Shang Tsung vowing revenge and Raiden deciding to prepare new warriors for a future Mortal Kombat tournament.
Shang Tsung wouldn't have had to sacrifice Sub-Zero if he simply had taken the Amulet of Shinnok, which was just lying around. The artifact is capable of summoning the Elder God Shinnok — a divine being who almost conquered all four realms with the object. In the right hands, the amulet could annihilate Raiden and unleash mayhem, something that has been close to happening on various occasions in the video games. The Amulet of Shinnok has often been the central source of conflict, and important characters such as Quan Chi, Havik, and Johnny Cage have been involved.
The Amulet of Shinnok resembles the Infinity Gauntlet in Marvel comics and the MCU. In the movies, the Infinity Gauntlet could be spotted for a brief second inside Odin's throne room in Thor. It only became the central McGuffin for all of the MCU until the post-credits scene of Avengers: Age of Ultron, preceding the events of Avengers: Infinity War, which was released seven years and 14 films after Thor. Loki and the Frost Giants could have taken the Infinity Gauntlet back in Thor (although it was later retconned as a replica of the real thing), but at the time, it was just an easter egg for eagle-eyed fans.
For now, the appearance of the Amulet of Shinnok in 2021's Mortal Kombat is just an easter egg, but the fact that Kano stole it could very well set up the main conflict of the entire live-action Mortal Kombat franchise. In fact, Kano once stole it in the video games, selling into to Mileena so she could defeat Kotal Kahn. Mileena dies, and the amulet starts changing hands until Shinnok is finally summoned. It wouldn't be a surprise if Kano's sleight of hand in the 2021 movie triggers s a similar chain of events and sets up the Mortal Kombat equivalent of Avengers: Infinity War.