WARNING: The following article contains spoilers for "Infinite Fury, Part II," a short story appearing in Captain America Annual #1 by Jed MacKay, Juan Ferreyra and VC's Joe Caramagna.
In the Marvel Universe, the Infinity Stones are growing into a major threat once again. After all six cosmic gems were united once more in 2018's Infinity Wars event series, the Infinity Stones were granted sentience and scattered across the universe. As a result, the multi-colored gems have started bonding with human hosts, imbuing them with all of their awesome, nearly-divine powers. Right now, three Infinity Stones have surfaced, the Time Stone and the Reality Stone -- whose human hosts are Hector Bautista, Quantum and Ripley Ryan, respectively -- while the three others remain unaccounted for.
In Captain America Annual #1, the quest to find the Infinity Stones heats up as Steve Rogers gets involved. In order to get some help, he calls in Nick Fury Jr., and their conversation reveals the existence of the Abaddon Index, a secret file that lists the eight biggest threats in the Marvel Universe.
In "Infinite Fury, Part II," Nick Fury Jr. answers Captain America's call for help in Texas. There, Steve Rogers quickly briefs him on the situation, by revealing that what they are dealing with has something to do with "the list." Upon hearing this mention, Fury knows exactly what "list" Steve is referring to: the Abaddon Index. When he first joined S.H.I.E.L.D., Fury was briefed by Maria Hill on this Index, which lists the eight most dangerous threats in the Marvel Universe.
A brief flashback scene shows us Fury first being briefed on the list, a screen that shows the most powerful cosmic and magical threats in the universe. This list, of course, includes the Infinity Stones, powerful cosmic gems which have been used to alter reality itself before, from snapping away half of all life in the universe in The Infinity Gauntlet to folding all of reality on itself to create the Infinity Warps reality. It's the return of the Infinity Stones that leads to the reveal that the Abaddon Index exists in the first place.
However, the list hardly stops there. At the top of the list is Galactus, the Devourer of Worlds. A powerful cosmic being from the universe that preceded the current, 616 Marvel Universe, Galactus feeds on entire planets to survive. He is a force of nature, one of the biggest threats in the cosmos, and he has visited Earth before. However, the threat of Galactus isn't all that pressing for the time being, given that he was recently killed by Thor.
Next on the list is Shuma-Gorath, a monstrous, demonic creature from the race of the Old Ones. Shuma-Gorath hails from another dimension, is millions of years old, and he is incredibly powerful. He has destroyed entire worlds and universes, and he has attempted to take over the Marvel Universe many times before. Presently, he is posing a tangible threat again in the pages of Savage Avengers, due to the villainous sorcerer Kulan Gath's machinations.
The Abaddon Index also features multiple villains who have clashed with the heroes of the Marvel Universe: Annihilus, Thanos, Apocalypse and Mephisto. Each of these characters has proved to be powerful adversaries on multiple occasions. Annihilus, an alien from the Negative Zone has a vast army at his command that he can use to invade, and he has great power thanks to the Cosmic Control Rod.
The Mad Titan Thanos has also long been one of the primary foes of the Avengers. Without any weapons to speak of, Thanos is a frightening enemy capable of destroying civilizations. He is most famous for assembling the Infinity Stones, which made him the most powerful being in the universe. And while he died at the start of Infinity Wars, Thanos is now back in the pages of Eternals, and he is growing powerful again. In fact, a recent vision experienced by Thor has shown that Thanos will grow more powerful and more dangerous than ever before, thanks to the Infinity Stones, the God of Thunder's own hammer Mjolnir, another, mysterious dark gauntlet and an army of Marvel zombies.
Apocalypse is one of the oldest and most powerful mutants in the world. The character has long been an enemy of the X-Men, but he recently joined forces with them to establish the mutant nation of Krakoa. While Apocalypse is extremely dangerous, he is currently not a threat. Indeed, he is now far away, living a life reunited with his wife and children in the dark realm of Amenth. As for Mephisto, he is the Marvel Universe's version of the Devil, a demonic presence that has long plagued the world. He has been playing an incredibly long game: the current Avengers comic series has recently revealed that Mephisto is the Avengers' oldest and greatest foe, and that he has aspirations to burn the entire universe.
Finally, the last threat listed on the Abaddon Index is partially hidden by Nick Fury's body. However, when looking more closely, one could recognize part of the Scarlet Witch's signature headband. The identity of this final threat remains to be confirmed, but it wouldn't come as a surprise that Wanda Maximoff would be included on this list. After all, she is so powerful in Chaos Magic that she is able to reshape the world as she sees fit -- both on a small scale, and on a large one.
Altogether, the Infinity Stones, Thanos, Annihilus, Galactus, Thanos, Mephisto, Shuma-Gorath and the Scarlet Witch are the biggest threats in the Marvel Universe, as SHIELD sees them. Nick Fury Jr describes them as threats that are "extinction level" -- beings and entities that all have the potential to destroy the world, if not the entire universe. And while the Infinity Stones are the clear and present danger, more threats from the Abaddon Index are on the horizon.