The film begins with Jane Foster, an astrophysicist introduced in 2011's Thor, being transported to an unknown realm in which the Reality Stone was contained for thousands of years. However, it absorbs itself into Jane's body and Thor bring her to Asgard for safe removal. Malekith, a determined warrior from an ancient race known as the Dark Elves, intends to use the Reality Stone and its universal scale of power to turn the Universe into darkness. Malekith gains possession of the Stone, but is killed by his ship falling onto him, and Thor sends the Reality Stone (in a container) with Asgardian soldiers to Knowhere, where The Collector will keep it in his collection.
Though the scene is not fully depicted in Infinity War, the Reality Stone is intercepted by Thanos on the planet Knowhere, and he then continues on his quest for the rest of the Infinity Stones.