Nick Fury collected Avenger DNA
How did G’iah and Gravik access the powers of all those Avengers? Well, after the fight against Thanos in Avengers: Endgame, Nick Fury employed several Skrulls to go to the battlefield and collect blood samples. He was able to get every hero and villain and kept them together as something called the Harvest. The Harvest was used to make G’iah and Gravik all-powerful but it’s unclear if there’s any more of it.
