Contains spoilers for A.X.E.: Judgment Day #2
Marvel Comics' new extinction-level threat is actually a creation of the Avengers. The corpse of the Celestial called the Progenitor has risen from death in Judgment Day, ready to extinguish life on Earth if he does not deem it worthy. This huge crisis, however, is a result of the Avengers abusing Celestial technology and resources in ways they should never have.
The Avengers' decision to use the corpse of a Celestial as their new base has always been controversial. Thanks to the prowess of the Wakandan engineers and consultancy from Alpha Flight, Black Panther and Iron Man not only made the giant inhabitable but also reverse-engineered part of its alien technology. While the Progenitor was technically dead, the team could still harness the cosmic being's power in various ways, including a global relay of teleporters and, even more impressive, technology for traveling through time and the various dimensions of the Multiverse. However, this does not mean that the Avengers fully understood the science of the Celestials, as has become painfully clear.
In A.X.E.: Judgment Day #2, by Kieron Gillen, Valerio Schiti, and Marte Gracia, a rogue faction of Eternals and Iron Man find the most unthinkable solution to stop the catastrophic conflict between the X-Men and the Eternals. Because the latter are genetically coded to follow the will of the Celestials, the group decides to bring the Progenitor back to life with a new soul and personality (encoded in a set of "holy scriptures"). This colossal endeavor is possible not only because the Eternals are of course familiar with Celestial technology but also because the Avengers have encountered and tried to harness it several times. Iron Man even piloted a dead Celestial once, so his body is used as a blueprint for the new god. However, disaster awaits when the Progenitor awakens and promises to "judge" the inhabitants of Earth for their right to live on the planet.
This situation would have never been possible if the Avengers did not choose to play with the technology of the gods, or even worse, at being gods themselves. The Progenitor, in fact, is not just a Celestial, but the source behind every superhuman power that ever appeared on Earth. It is a being of cosmic significance for the history of the planet, and yet the Avengers decided to turn it into a palace first, and then play Frankenstein with it. This should not come as a surprise, however. The Avengers are using Celestial technology to pursue Mephisto throughout time, despite barely knowing how to make it work, unaware of the consequences it could have for the Multiverse. The rise of the Progenitor is, in fact, only the last straw, and now Earth will have to pay for the Avengers' mistakes.
While Marvel has recently done a lot to demystify the Celestials, they are still some of the most powerful beings in all creation, whose existence is tied with the origins of the Multiverse itself. Recklessly trying to harness their technology and potential is something that could be expected from villains, not heroes like the Avengers, who should have instead treated the Progenitor with religious deference.