Thousands of years before HYDRA found the Tesseract, before the Avengers came together to protect the world, there were other heroes. These heroes practiced sorcery in secret, learning how to defend those who could not defend themselves from one of the six infinity stones. One of these heroes, Agamotto, created three mystical objects that contained power from these stones, and he called them Mother Boxes.
But then, someone came for our world. A great armada appeared in the sky, laying waste to all who opposed it. The leader of the invasion was a being called Darkseid. A name cursed and feared in every universe. Darkseid was met in battle by Earth's defenders: the Old Gods, men, Atlanteans before their descent into the sea, Amazons before their betrayal and enslavement, and guardians from the stars. Their histories had taught them not to trust each other, not to hope for an alliance, to fight apart. As Darkseid waged war on Earth, he found a secret there. A power hidden in the infinity of space: the Anti-Life Equation, written into the surface of Earth. He had been searching for that equation for centuries, looking for a way to control all in the universe. But with only part of the equation, he could only control a select few. He called forth the mystics who worshipped and controlled the Mother Boxes. To conquer, the three Mother Boxes have to join and synchronize into the Unity. The Unity cleanses a planet with fire, transforming it into a copy of the enemy's world. All who live become servants of Darkseid, alive but drained of life: parademons. But before the Unity could synchronize, the defenders of Earth fought and attacked as one. Amazons alongside Atlanteans, Zeus and his son Ares alongside the guardians from the sky. A golden age of heroes fighting together to defend life on Earth. They did what no world had ever done: sent the enemies back into the stars. The three Mother Boxes never synchronized. The Unity never came to pass. But in their retreat, the Boxes were left behind on Earth. They grew weak: dogs without masters falling asleep, awaiting their return. Falling from the view of the enemy, anonymous among a trillion worlds. The defenders of Earth made a vow: Men, Atlanteans and Amazons, each would enshrine and guard one of the three sleeping Mother Boxes according to the rites and rituals of their cultures, in case a Box should ever wake again to call out to the planet Apokolips to return and conquer the only world Darkseid had ever lost.
But now, one of the boxes has awoken.
With Superman's resurrection, Darkseid can feel the presence of the awakened box. And he will not stop until it is his.