Invincible's Season 4 finale serves as an epilogue to the epic Viltrumite War, following Mark Grayson as he returns to Earth. However, scarred by recent events, the young hero can't help imagining the horrific acts the Viltrumite leader, Thragg, might inflict on Eve, Debbie, and Cecil.
The hits keep coming—even if they're just of the emotional variety—as Eve tells Mark that she had an abortion while he was in space. Her powers have returned, and she assures her traumatised boyfriend that she's going nowhere.
Nolan, meanwhile, has also returned to Earth and, after revisiting the mountain where he very nearly beat his son to death in Season 1, the contemplative former villain manages to convince Debbie to accompany him to Telescria. There, she can be by Olvier's side while he heals from his beating at Thragg's hands.
Talking of Telescria, Allen the Alien learns that, at Thadeus' behest, he's been appointed the new leader of the Coalition of Planets. However, the council is resolute in their belief that the only way to protect the universe is to kill all Viltrumites, including Nolan and Mark. That's easier said than done, but his predecessor had a plan.
Later, when the early warning system meant to detect a Viltrumite invasion is activated, it reveals that the Viltrumites are already on Earth.
Thragg meets with Mark and offers him an ultimatum. If he allows his people to remain on Earth and quietly repopulate the Viltrumite Empire—as Nolan did with Mark once upon a time—they won't harm a single human. However, the moment the show's title hero interferes, they'll slaughter billions of innocent people and enslave the rest. Rather than let his home be conquered, Mark is forced to agree.
In a mid-credits scene, we learn that Thadeus created a "terrible weapon" before his death. His new Scourge virus (the original nearly made the Viltrumites extinct) can kill Thragg and his people for good.
However, in wiping them out, Mark and the entire human race will also die, leaving Allen with quite the decision to make heading into Season 5.
Talking to Entertainment Weekly, Thragg actor Lee Pace shared his take on the deal that's made between the villain and Mark:
"There's a measure of respect in it, "and I think there's a measure of, 'You're here, I'm here. You're gonna have to deal with that, and I'm gonna have to deal with you, but I can't kill you yet, and you can't kill me, period.' So I think that's what it is, because he could just do it without even telling Mark that he was gonna do it. It's what Mark's been doing. So he could just surprise Mark with suddenly people are popping up with powers, but he's not doing that. He's doing this, and it's direct. He's saying, 'I rate you as a powerful, significant person. You could be the hero of this story.' So I'm gonna look at you dead in the eye and see what you're made of and see what you do with this.'"
He added, "Maybe Mark will be an ally at some point. He doesn't know that. All he knows is that he's gonna do this, and he's gonna do what he needs to do to get where he wants the Viltrumite people to be."
Invincible Season 4 is now streaming on Prime Video.