Darkseid is one of the few DC Comics villains who doesn't primarily belong to just one hero. The lord of Apokolips has proven to be a threat to the entire DC universe on numerous occasions, so although there are times he tangles with the likes of Superman or Wonder Woman on their own, he's generally considered to be the arch-nemesis of the entire Justice League. However, the Justice League movie opted to use Steppenwolf, Darkseid's uncle, as the main antagonist, and Darkseid was only mentioned once during the story. As it turns out, though, Justice League's flashback battle was originally centered around the Anti-Life Equation, thus providing a more direct link to Darkseid.
For those unfamiliar with Jack Kirby's Fourth World mythology, the Anti-Life Equation is a mathematical formula that, should someone solve it, would allow them to gain total control over all sentient beings in the universe. Darkseid is already one of the most powerful beings in existent, but he's obsessed with piecing together the Anti-Life Equation so that he can erase all free will. In the comics, he's frequently targeted Earth because he believes part of the equation reside in humanity's subconscious. It turns out this was the original reason for Steppenwolf and his Parademon army invading Earth thousands of years ago in Justice League, as revealed by Weta Digital, which handled the visual effects for that sequence. among other things. However, something changed during the creative process, and in Justice League's theatrical cut, Steppenwolf instead came to Earth with the three Mother Boxes to terraform our planet into a copy of Apokolips, something he tried to do again in the present.
Obviously the inclusion of the Anti-Life Equation in Justice League wouldn't have meant anything to casual moviegoers, but for the hardcore DC Comics fans, this would have been a great nod to Darkseid. It also begs the question of if the Anti-Life Equation would have replaced Steppenwolf's goal of completing the Unity. Regardless, the plot element was cut out, and the wait continues to see Darkseid debut in the DC Extended Universe. Still, Justice League wouldn't have been the first time that the Anti-Life Equation has been hinted at in the DCEU, albeit indirectly. Earlier this year, director Zack Snyder stated that the reason Superman is evil in Batman v Superman: Dawn of Justice's Knightmare is because he became susceptible to the Anti-Life Equation.
It remains to be seen if Justice League 2 will move forward, but Ava DuVernay is working on a New Gods movie, so presumably that will be out next opportunity to learn more about Darkseid and his ilk in the DCEU. Stay tuned to CinemaBlend for continuing coverage, and look through out DC movies guide to find out what other DCEU projects are in development.