In the 2018 film Avengers: Infinity War, the villainous Thanos (Josh Brolin) was seen acquiring the all-powerful Infinity Stones, eventually using them to wipe out half of all life in the universe.
Their story is entwined with another Marvel species known as Celestials, who are connected to the Infinity Stones.
Showing up at the start of Infinity War with the Power Stone already in his possession, Thanos mentions he took hold of the stone during his attack on the planet Xandar.
Eternals focuses on a group of immortal aliens known as the Eternals, who have secretly been living on Earth for thousands of years.