Vormir is a remote and barren world and the whereabouts of the Soul Stone that appears in Avengers: Infinity War and Avengers: Endgame.
Background
Vormir's only known inhabitant is the Stonekeeper. The Stonekeeper guides the ones who come searching for the Soul Stone, but warns them that the price to obtain the stone is very high: the life of a loved person, a soul in exchange for a soul.
Appearances
Avengers: Infinity War
Gamora found a map that lead Vormir years ago; however she destroyed it. Allowing her to get away with the lie that she never found it, Thanos always believed she remembered the location.
In 2018, Thanos forced Gamora to take him to Vomir to get the fourth Infinity Stone by threatening her sister Nebula. Once on the planet, the Stonekeeper tells Thanos that to get the stone he must sacrifice a loved one; a soul for a soul. Gamora laughs at him, since Thanos doesn't love anyone. However, she finds him crying; the Stonekeeper states they are not for Thanos. Gamora quickly realizes Thanos loves her and despite her struggling, he toss her off the cliff and gets the Soul Stone.
Avengers: Endgame
Vormir is visited by Hawkeye and Black Widow, when they time travel to get the Infinity Stones from 2014. On Vormir, the two of them fight over who will be sacrificed for the Soul Stone, because both of them prefer to sacrifice themselves over losing their best friend. In the end, Black Widow outmaneuvers Haweye and sacrifices herself so her friend can obtain the stone. After the Avengers used the stones to bring back the half of life in the universe that was erased by Thanos and then defeating the Mad Titan, Captain America time travels to return the Soul Stone to Vormir.
