Everything that happened during the events of Avengers #1? It's all the fault of the Avengers from 1,000,000 BC. That's what Marvel's Free Comic Book Day offering has to say.

In Marvel Legacy #1 back in September, a prehistoric version of the Avengers made their debut. This team included counterparts to the modern day team, including a young Odin, the first Iron Fist, a Black Panther, a Hulk-like Starbrand, the Phoenix, and a Ghost Rider who rode a woolly mammoth. These heroes came together to fight off the Fallen Celestial, but what came after doomed the Earth to a terrible attack one million years later.

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This is a story by Jason Aaron and Sara Pichelli that fills in between the panels of Avengers #1. It's the #0 issue you didn't see coming, but it also propels us into the future of Aaron and Ed McGuinness' run on the title.

The Confession One Million Years in the Making

The issue starts off with something of a confession. Black Panther has never met Odin, the god king of Asgard before, and yet Odin knows him. T'Challa's ancestor once fought at Odin's side, so the Asgardian feels something of a kinship with the king of Wakanda. Maybe this is why he asks Black Panther to meet with him in secret among the ruins of Asgard. This is where he confides in "an old friend" about the mistake the BC Avengers made all those years ago.

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It would seem that simply killing the Fallen Celestial (if they could even accomplish that) was something of a mistake on their part. In the heat of the moment, this cosmic being may have seemed like a force of destruction, but it was also clear that the Celestial was sick. Perhaps they could have helped it instead of hurt it. The BC Avengers, not knowing what else to do, buried the gigantic lifeform and tried to forget about it. Unfortunately, secrets can only be hidden for so long, and even after a million years, the truth has to come out.

The Black Panther of 1,00,000 BC warns the group that by killing this sick Celestial now, they may have made the world a target. "I fear what next will come from the sky. This time not mindless. But sick only with vengeance." And as the first Black Panther foretold, some unknowable cosmic force has come to Earth in the present day, and though we don't yet know how, it's clear that the two events are connected. Revenge has arrived.

 The Fate of the Fallen Celestial Revealed

Remember the Fallen Celestial? Back in Marvel Legacy #1, Loki discovered the cosmic being still living under ground in modern day. It was calling out for the Final Host then, who just now arrived in Avengers #1. Loki seems to have aligned himself with the Celestial for some unknown reason, but as the God of Mischief does he really need to explain why he's messing with his father's legacy?

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It seems that Loki was the one who helped summon the Dark Celestials to Earth, and now he has taken the Fallen Celestial with him. Just like old times, it would appear that the mischief of Loki has brought the Avengers together again. At this point it seems like fate, that when he starts trouble, the Earth's Mightiest Heroes will be there to stop him. However, Loki is going to be packing some serious reinforcements this time around.

The reason the Fallen Celestial is no longer underground for Black Panther to find in Avengers #1 is because Loki had already brought it with him to meet with Odin. It was their attack on him that prompted Odin to seek out T'Challa and request something of the hero. The god knows his son has caused more trouble than he should be allowed to get away with. However, even after everything, Odin doesn't have the heart to do what must be done. He asks that the Black Panther finally kills his son once and for all.

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What Other Threats Are to Come?

If you can believe it, the Fallen Celestial and the Final Host are not the only things standing in the Avengers' way. The team from 1,000,000 BC noticed that the cosmic being seemed to be sick, as if it were infected with something. Perhaps their biggest mistake was not taking the time to heal the sick. When Black Panther travels to South Africa to investigate where the Fallen Celestial was once buried, he and Doctor Strange discover what appears to be the source of the infection.

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In the million years since space giant came to Earth, it would appear that whatever was hindering the Celestial has now taken root deep within the heart of the planet. Bug creatures have laid millions of eggs and now they seem to be ready to attack the surface world, but what are they? Marvel Legacy #1 left us a clue. Just before Starbrand exploded during his fight with Robbie Reyes, he revealed something of a prophecy, stating, "The sleeper will wake. The horde will feed," and then something about the Final Host arriving.

If the sleeper is the Fallen Celestial, and the Final Host are the Dark Celestials at the end of Avengers #1, then that must mean these bugs are the Horde. That name has been used in association with a swarm of cosmic insects introduced in Neil Gaiman and John Romita Jr.'s Eternals series a decade ago. These bugs are something of a universal opposite to the role the Celestials play in the cosmos. If the Celestials are the builders, the Horde are the devourers and the destroyers.

Maybe by sealing away the Fallen Celestial, the Avengers of 1,000,000 BC have allowed Earth to become threatened by an unknown and unseen force within the planet itself. The Final Host could be here to wipe out the Horde, and the Earth with them, and it's all the fault of the prehistoric Avengers. As Odin says, maybe it would have been better to do nothing and let the world die after all.