Most Marvel fans can probably list all of the Infinity Stones by memory, but they would probably be shocked to learn there was a forgotten stone that was created just to kill Thanos. This happened in the 2015 Secret Wars tie-in The Infinity Gauntlet. It was written by Gerry Duggan and illustrated by Dustin Weaver.
On God Emperor Dune's amalgamated planet Battleworld, there is one realm that has been overwhelmed by a swarm of bloodthirsty bugs. They were released as a plot by Thanos to collect all of the Infinity Stones. Initially, he tricks a girl named Anwen to help find the stones with her family. Eventually, Thanos betrays the family and keeps five of the stones for himself. The only stone he needs to complete his gauntlet is the Reality Stone, which Anwen uses to battle him.
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The fight does not go well. Despite creating an impressive mechanized armor with her family, Anwen is defeated. It seems all hope is lost and Anwen decides to hand the Reality Stone over to Thanos. He places it in his gauntlet, believing he has collected all of the stones. But something goes wrong. As Thanos's body begins to disintegrate, Anwen reveals she used the Reality Stone to create a new stone that looked exactly like it. This stone is called the Death Stone and it causes Thanos to die when he adds it to his gauntlet.
This was the first appearance of the Death Stone and it has only appeared one other time since. During Contest of Champions, Thanos enlists Corvus Glaive and Proxima Midnight to trap the Marvel heroes within the Death Stone. He does this so that he can collect the other stones without their interference. However, this only occurs in the Contest of Champions game,
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